A tie-in to a sewer pipe is necessary when installing an internal or external household sewer for a new home, to divert storm water to a sewage treatment plant, to connect a new plumbing fixture (sink, dishwasher or washing machine). A skillfully executed tie-in will help to avoid a radical replacement of the elements of the existing sewer.
Approach methods
Inserting a new branch into a sewer pipe involves connecting an apartment or house to a local sewer, to vertical risers or a horizontal bed. There are many ways to properly and reliably make eyeliner. And the building materials market offers a large selection of various devices in the form of adapters. But for the sewer to work properly after the tie-in, you need to know what are the simplest ways to make a tie-in into the sewer without involving expensive specialists, but doing all the plumbing work yourself.
Inlet to plastic pipeline
When starting to insert into a sewer pipe, one must prepare for the fact that the work will be dirty, which means that you will need to wear overalls. Before starting the process, you need to learn that all horizontal connections must have a slope.
The amount of slope will depend on the diameter of the workpiece:
- for diameter 50 mm optimal slope - 3,5%;
- for 110 mm – 2%;
- for 160 mm – 1%.
It is not recommended to make slopes of a larger size (counter slopes), since silt deposits will settle on the inner walls, narrowing the clearance. It is more rational to cut into a horizontal pipeline from above, so there will be fewer blockages and possible leaks during operation.
To enter a new wiring into an existing one, you need a branch pipe (a small piece of pipe) and clamps that will play the role of fasteners. After all the necessary parts have been purchased, you can begin to work on tie-in PVC sewer pipes.
Sequencing
Work must be performed in the following sequence:
- Close the sewer outlet.
- Drill a hole in the plastic wall for a new input.
- Fix the pipe in this hole.
- Insert a corrugated rubber seal inside the pipe.
- Fasten the joints with a clamp and tighten with a screw connection (attached to the clamp in the kit).
- Insert a new sewer line into the outlet pipe.
The clamp can be bought ready-made, or you can make it yourself. For self-production, you must perform a number of actions:
- Take a plastic blank equal in cross section to the existing pipeline.
- Cut off a piece of the required length from it.
- Saw lengthwise.
- In one half, drill a hole equal in diameter to the new pipe.
- Glue the outlet pipe into the gap.
- Treat the joint with a hermetic compound.
- Attach the clamp to the hole cut in the existing pipe (glue and seal).
- Connect to the second component of the clamp.
- Fasten with wire.
Tee application
A tee is needed to supply several additional sections to the main sewer. When inserting a new sewer outlet into PVC sewer pipes, tees are rarely used, since joining two plastic parts in this way is fraught with depressurization of the connection zones. Such adapters are more often used in the case of insertion into cast-iron wiring.
When tapping into a sewer pipe using a tee, you must perform the following steps:
- Buy a straight tee.
- Shut off the existing sewer.
- Cut out the section of the cast-iron pipe where the supply will be carried out.
- Install a tee.
- Lead the supplied systems into the holes of the tee (this must be done as deep as possible).
A special bracket is used to fix the input wiring in the desired position. The main difficulty may be connecting the existing wiring to the tee if the cast iron system is old. Old outlets are often located close to the floor and can be difficult to access due to tiling. It is difficult to make a joint when the pipes fit snugly against the wall. All these reasons impair access to the attachment point.
Gaps and joints of joints are protected with sealant. High-quality sealing materials are silicone fillers, epoxy resins, special sealing tapes that are very popular now. Before sealing, the cast-iron joint must be cleaned of grease, dirt, old waterproofing, after which it is possible to wrap the part of the existing wiring with a new tee with two layers of sealing tape.
Application of the adapter
A plumbing adapter is a device that is designed to join pipelines that do not have a convenient connection. The method of tapping into the sewer using an adapter is used when it is necessary to connect additional plumbing (for example, a washing machine), and it is not possible to disassemble or cut the existing pipeline.
Such a connection is possible only in a PVC sewer pipe, in which a hole is cut out according to the size of the incoming branch. The adapter has the form of a cap with a tap for the plug-in input. The introduced pipeline should be much smaller in cross section than the main one (at least 2 times). This requirement is a disadvantage, since it is necessary to have just such a ratio of the main and supply wiring.
The procedure for performing work on tie-in into a sewer pipe using an adapter:
- Turn off the water.
- Dry the pipeline.
- Drill a hole equal to the diameter of the adapter (if the diameter of the existing pipeline is 50 mm, the hole for the adapter should be no more than 22 mm, with a cross section of 110 mm, the supply should be 50 mm in diameter).
- Insert the adapter into the prepared hole.
- Cover the adapter with sealing material.
- Fasten with a clamp.
- Insert a rubber seal (cuff) into the outlet of the adapter.
- Install new pipeline.
Entrance to the sewer plastic riser
By connecting sewer outlets to existing risers, you can purchase all the parts and elements necessary for work at a plumbing store. The kit will include blanks of the desired section, connecting cuffs, rubber gaskets, clamps. But you need to know that when making a tie-in into the riser, an additional supply system will act on it with an increased load.
To cut the pipeline into a vertical sewer riser, you need to purchase a compensator. A pipeline compensator is a device that reduces the harmful effects on materials, reduces the load on structures, prevents various negative effects from pressure and vibration, thereby extending the working life of the sewer system.
To bring the connection to the sewer riser, you must have an adjustable socket for the required number of outlets and home-made or ready-made clamps.
Having everything to do the work, you can start eyeliner:
- Define a cutoff point.
- Cut out part of the riser for the new pipeline.
- Install the compensator and tee tightly in the upper part of the riser.
- Treat all connecting seams with sealant.
- Bring the necessary systems to the tee.
- Attach the sewer riser to the wall using clamps as fasteners.
Or a toilet bowl - in all of the above and other similar cases, you can not do without creating additional water intake points. And for this it will be necessary to organize new working outlets from the main sewer pipe. There are several options for connecting to the system - then we suggest with photos and videos to consider how to properly crash into a plastic sewer pipe in the three most common and reliable ways: using a tee, an adapter and a saddle.
Tee tap
If a pipe that exactly matches the diameter of the main sewer pipe cuts into the outlet system, a standard tee can be used to connect.
For work you will need: a hacksaw, a file, a plastic tee with a plug, silicone sealant and a special compensating pipe - a piece of pipe with a transitional diameter.
Tees for tapping into sewer pipes
Before proceeding with the tie-in, it is necessary to determine the height of the tee as accurately as possible. The latter should be located at such a level that the pipe connected to it is at a slight slope - such a position will ensure the effective discharge of sewage into the general system.
Advice. Use a tee with an angled pipe connection to the drain side - such an insert will reduce the risk of sewer blockages in the system.
After the preparatory work, you can proceed to a direct insert into the sewer:
- Cut a piece of sewer pipe that exactly matches the length of the tee to be connected.
- File the inside of the pipeline with a file to remove any burrs.
- Treat the outside of the pipeline with sealant.
- Put a compensating pipe on the first truncated sewer pipe - push it from bottom to top with a wide part.
- Mount a plastic tee on the second truncated pipe.
- Treat the narrow part of the compensating pipe with sealant and press it tightly into the socket of the tee.
Sealant treatment
- Seal all pipe and tee connections.
- Put a cap on the tee.
Tapping with an adapter
Often it is not possible to cut and disassemble a sewer pipe for one reason or another, but it is still necessary to organize new branches. How to be in this situation? The best option is to use an adapter. This device has the form of a cap with outlets for the connected pipe.
Important! When deciding to use an adapter, please note that it is designed to connect only those pipes whose diameter is half the diameter of the main sewer pipeline.
To tap into the sewer using an adapter, you will need a file, a drill with a crown, an adapter cuff, silicone sealant, clamps and. The work is carried out according to the following scheme:
- In the radius of the cutout for the adapter, clean and thoroughly dry the working surface of the pipeline.
- Using a core drill, drill a hole in the pipeline for the adapter.
- Prepare the fitting, treat it with sealant and fix it on the plastic pipe with clamps. It is not necessary to tighten the fitting all the way so as not to deform the plastic.
- Insert the cuff-adapter into the fitting branch pipe and connect the adapter to it, having previously lubricated it with silicone sealant. It is important that the connection between the cuff and the adapter is as tight as possible, otherwise leaks and disruption of the sewer pipeline cannot be avoided.
Tapping with an adapter
If the sewer pipe into which the new outlet cuts is located horizontally, the adapter must be connected with a slope of no more than 45 degrees from the vertical.
Insert with saddle
The easiest and fastest way to crash into a plastic sewer pipe is to use a saddle. This is a variation of the compression fitting, the design of which can be presented either in the form of a clamp or in the form of an overlay. In the first case, we are dealing with a crimp that tightens the sewer pipe from both sides, and in the second, with a small lining that is welded onto the pipeline. As practice shows, a crimp clamp is more reliable and practical, so it is better to use it for tie-in. Such a saddle can either be selected for a specific diameter of the sewer pipe, or be universal - providing for the possibility of adjusting the coverage of the clamp depending on the size of the pipeline.
The saddle can be mounted on the pipe in two ways - by welding or tightening. But in both cases, the installation scheme is quite simple to execute:
- Determine the location of the tie-in and drill a hole in the pipe corresponding to the diameter of the outlet of the saddle used.
- Alternately put on the sewer pipe the upper and lower halves of the saddle. Make sure that the rubber gasket of the upper half sits tightly on the hole in the pipe.
Insert with saddle
- Connect the two halves: weld them or tighten them on the sides with special fasteners that come with the device.
- Seal all joints with silicone sealant.
Thus, we have three ways to crash into a sewer plastic pipe: a tee, an adapter and a saddle. Whatever option you choose to connect to the system, do not forget that only a well-done job will make it possible to install a new outlet without hassle - do not neglect the proposed instructions, and then you are guaranteed a high-quality tie-in to the sewer.
It is almost impossible to correctly calculate and install the required number of tees in the sewer pipe at the construction stage. In the process of putting the premises into operation, residents will certainly need to install additional devices that require connection to the sewerage system.
Insertion into a metal riser
In this article, we will consider the basic principles that guide the work on tie-in into a sewer pipe. Let's talk about the necessary tools and materials that may come in handy.
When is a sewer connection necessary?
There are many situations in which a tie-in into a sewer pipe is the only correct solution. The most common are the connection of new plumbing equipment or the transfer of old to another place, the installation of washing machines, automatic sinks and other electrical equipment with automatic draining. A tie-in may also be required when connecting a private system to a central sewer. In this case, the work must be coordinated and carried out by employees of the public utility. Otherwise, the connection will be considered illegal and punishable.
In some situations, an alternative to tie-in to the sewer can be the installation of a splitter that adds connection points to the sewer.
Types of sewer pipes
For the construction of sewer lines, PVC pipe systems are mainly used. A plastic pipe is more practical, has a longer service life and is much cheaper than metal counterparts.
PVC drain 110 mm Additionally, PVC systems can be upgraded at any time, because manufacturers offer a large selection of tees, branch adapters and fittings, with which you can cut into a sewer drain pipe at any stage of construction or after the premises are put into operation.
In old houses that were built during the time of the union, cast-iron drains were used as sewers.
Cast iron sewer system Currently, they are rare, because. most homeowners and utilities have already replaced them with plastic. Where cast iron is still left, it will take more time to tie in, because. you will have to use complex tools, up to a gas cutter.
In some cases, metal and metal galvanized pipes are used for sewage. Like the previous option, they are less practical than their plastic counterparts, and for self-insertion into them, you will need to have the skills of a welder.
Tools required for work
An insert into a plastic sewer pipe is carried out using an additional tool. For those who plan to carry out the work on their own, you will need to have:
- Electric drill or screwdriver. For drilling a hole in a plastic pipe.
- A set of crowns for plastic or wood.
- Bulgarian with a hard-alloy disk.
- Stationery knife, for cleaning edges.
- Sealant gun.
- A hacksaw, jigsaw or other similar tool with which you can cut a plastic pipe.
- Welding machine (when working with metal pipes).
- Gas cutter (when working with cast iron pipes).
And of course, you will need a hammer, tape measure, pencil and other small tools that every self-respecting owner should have.
General principles of insertion into the sewer drain
An insert into a sewer pipe, no matter what type it is, is done in compliance with the basic principles of installation. The main rule is that the connection must be completely sealed. Otherwise, smudges or the penetration of an unpleasant odor may occur at the installation site of the tie-in, which is quite unpleasant.
Important! To seal additional tees or tie-ins, we recommend using raw rubber or silicone plumbing sealants.
The connected pipe should not go deeper into the main line by more than 0.5 mm. Otherwise, the risk of blockage at the installation site of the tie-in increases. This is the second rule to follow.
The next important point is related to the level of the connected drain. For proper functioning, the connected structure must be slightly higher than the main drain (for horizontal versions). The insert into it is carried out in the upper part.
In vertical systems, the side from which additional equipment is connected does not matter; in this case, the principle “as convenient” is followed.
Fittings for PVC sewer systems
For tie-in to the sewer system, it is convenient to use special fittings. For convenience, we divide these devices into several types.
Splitters
Designed for connection to the sewer system, they have several outlets of the same or different diameters for connecting drain pipes.
Splitter 110 mm Splitters do not require additional waterproofing, because. they have a rubber or silicone seal. To install such a fitting, it is required to completely cut the main pipe, which in some cases is impossible. This type includes tees and crosses with different connection angles.
Sidebars
For connection to a non-pressure sewer system, you can use "tie-ins". This is a device that is installed in a pre-prepared hole of a certain diameter and does not require a complete cutting of the pipe. 110/50 tie-ins are widely used, which are used to connect a sewer pipe with a diameter of 50 mm to a 110 mm system. The device does not require additional waterproofing, because. has a rubber seal, which, when properly installed, reliably seals the connection.
Mortise 110/50 with key Included with the factory PVC "tie-in" should be a wrench that is used to tighten the part during installation. Without such a key, it will not be possible to correctly install the "insert".
Saddles
The device works on the principle of a clamp, it is installed on top of the main pipe and clamped with a bolted connection.
Saddle tie-in Can be used for both PVC and metal systems. For installation, it is not necessary to make a cut in the main pipe, it is enough to prepare a hole, the diameter of which is equal to the diameter of the connected pipeline.
Couplings
A fitting of this type is designed to connect the main pipe to an embedded tee or cross. It is mainly used for systems in which it is not possible to push the main pipe apart at the cut point. Couplings are produced in two types, compensating and slip-on. It is convenient to use both options depending on the situation. Additional waterproofing is not required, because. have a standard o-ring seal.
Sliding coupling Mortise in horizontal system 110/50
This type of insert can be made in several ways. Depending on the situation, you can use any of the options described below, because. They are all field tested and guaranteed to work.
With factory cut
It is convenient to connect a drain with a diameter of 50 mm to a pipe of 110 mm using the factory "tie-in" 110/50. To do this, according to the manufacturer's instructions, a hole with a diameter of 57 mm will need to be drilled at the connection point. You can make a hole with a drill and a core drill. Next, the "tie-in" is installed in the mounting hole and tightened using the wrench supplied with the fitting.
With the help of a double
The second option, in which you can do without a special mortise fitting, is to use a regular double 110/50 at 90 degrees, which is pre-cut lengthwise.
Correct fitting cut It is necessary to prepare a hole in the main drain, where it is planned to connect an additional pipe. The diameter of the hole must be at least 50 mm and not more than 60. The shape of the hole should not be perfectly round, therefore, with this method, a grinder can be used to make it. The cut off part of the fitting is installed on the main pipe with an overlap and fixed with ordinary plumbing clamps. Raw rubber or sealant can be used as an insulator. This method is convenient because it does not require a complete cutting of the main pipe.
With splitter and connecting fitting
In the case when it is necessary to cut a pipe of equal diameter into the main drain, the two previous methods are not suitable. A splitter is required.
Splitter with expansion pipe This method of inserting into a plastic pipe allows you to mount a splitter in a partially underground pipeline. The diameter of the connecting outlets of the splitter must be equal to the diameter of the main pipe, this requirement must also be met for the connecting fitting.
All that needs to be done is to cut a section from the main pipe equal in total to the length of the splitters and half the length of the connecting fitting. Next, clean the edges, grease with soapy water and install the fittings. First of all, the connecting element is installed and shifted so that it is possible to install the splitter. Then a splitter is put on the main pipe and the previously installed fitting is shifted back, connecting everything into a single sealed system.
The main points of insertion into a vertical riser
The previously described methods of connecting to a plastic pipeline can also be used for vertical risers. It is important to understand that if the drain pipes can be slightly moved apart, then for tapping the splitter, it is not necessary to additionally install a connecting fitting. In rigid pipelines, a connecting element is required.
When working on a tie-in into a vertical riser, it is necessary to warn the neighbors in advance about the ongoing repairs and ask them not to use the sewer if possible. For insurance after cutting the riser on its top, it is better to secure a bucket into which the feces will merge, otherwise they may spill on you.
Today, almost any plumbing work is, albeit a difficult matter, but it is quite predictable. That is, you can approximately calculate the budget, and possible deviations, and the timing of the project.
And all because modern materials have appeared on the market, which are very convenient to work with and which allow you to do plumbing not with torment, but with interest. We can say that the fittings and adapters that exist today have turned this business into a kind of constructor, the main difficulty of which is to create a truly high-quality connection of parts.
Such common work as a tie-in into a sewer riser is no exception. Now this is done quickly, reliably and inexpensively. Moreover, it does not matter what exactly the main branch of the sewer is made of.
Let's look at the difficulties that craftsmen had to face earlier when working independently, before the advent of modern technologies.
| riser type | Standard difficulties and their causes |
| 1. Cast iron. | As a rule, a tie-in into a sewer riser of this type was dangerous at least because the entire line as a whole could collapse when the desired section was dismantled. This happened quite often and mainly because dismantling was most often carried out with a hacksaw and a hammer. Now everyone can afford to buy a grinder for such work, which allows you to do without any strikes on the metal at all. |
| 2. Steel. | In this case, it was also difficult to do it yourself, without the help of specialists and a large set of tools. Simply because steel, unlike cast iron, cannot be broken with a hammer. And with a hacksaw for metal, it was not possible to cut far from the entire circumference of the pipe. Here autogenous and other similar cutters usually came to the rescue, which would hardly have been found in the arsenal of a home master. |
In addition, there was one more detail, because of which the installation itself was difficult - most often it was impossible to do without welding to connect the parts. And this is a very serious obstacle to independent work, you see.
Please note that we did not analyze the work with plastic material in this table.
Simply because such technologies have never been used in our country before.
However, step-by-step instructions for working with such pipes will be published below.
And now it’s worth considering in detail what tie-in methods exist now - you yourself will see that modern methods are much simpler, safer, cheaper and more efficient.
Self-tie-in to the riser
Before starting, it is worth noting that we will analyze only those methods that are most easy to implement on our own, and the price of which is affordable for everyone.
The only difficulties that may arise when performing the work described below is the need to invite a welder at some stage. However, you must admit that now it is not difficult to do this - there are many offers on the market. Moreover, such services will be needed for a very short time (maximum for half an hour).
Well, now let's start the review of the practical part.
Working with plastic
What makes this material uniquely convenient is its ease of processing and low weight. Such pipes are easily influenced by an ordinary hacksaw, and the connection is made either using a special soldering iron, or generally mechanically.
Tapping into a riser of this type, as a rule, is carried out by the second method.
It's done like this:
- A special tee is bought with the same diameter as the pipes on the riser.
- A fragment is cut out at the desired section of the highway, which should be several centimeters shorter in length than the length of the fitting.
- The cut edges are cleaned with fine-grained emery or grinder. This is done in order to make the lines of "docking" as smooth as possible.
- The edges of the highway are lubricated with ordinary sunflower oil. The same is done with the inner rim of the tee. If all this is not lubricated, then subsequently it will be difficult to fully connect the parts.
- The riser pipes are inserted into the tee. But since, by default, the distance between the cut edges is less than the length of the adapter, a special approach is needed here. The extreme points of the riser are slightly retracted to one side and slightly inserted into the fitting, and then gradually reduced into one straight line and sunk deeper and deeper into the tee.
Such is the scheme.
Please note that before crashing into a sewer pipe (regardless of what it is made of), you need to warn the neighbors from above that the bathroom or kitchen drain cannot be used during such and such a period of time.
Otherwise, you run the risk of at least getting dirty during work, and at the maximum, poor-quality organization of the connection due to moisture entering the work plane.
Now about working with metal structures.
Connection with cast iron and steel riser
An insert into a cast-iron sewer pipe is performed according to this principle:
- The grinder cuts out the desired fragment of the riser. If the disk does not reach any point of the circle, then it is very undesirable to complete such dismantling with a hammer due to the fragility of the cast iron. It is better to try to finish the metal with a cloth - it will take more time, but the riser will remain intact. (See also the article.)
- On the part of the pipe that is less mobile (usually the one that is shorter), the tee is slightly pushed on and tilted to the side. A more mobile pipe is also directed in the same direction, which is then also baited onto the tee.
- The riser line is gradually leveled, and the pipes are sunk deeper into the tee.
As you can see, the diagram is very similar to the previous instruction. However, this method may not work if the sewer pipes cannot be moved. Indeed, in such a situation, it will simply be impossible for them to wear a tee.
A tie-in to the sewer pipe may be required for any person who, for example, decided to install another drain pipe in his apartment or an additional sink, or simply bought a new dishwasher or washing machine.
1
There are several different methods of tapping into the pipes of the water and sewer system. The modern market offers a huge selection of various transitional devices that make this process as simple as possible.
The most commonly used method involves the use of a special tee. Its application requires the removal of a small part of the pipe after sawing it.
The specified section of the tubular product along its length must be the same as the tee, which is supposed to be installed on the cut piece of the pipeline. This method is usually used for metal pipes. At the same time, the mounted tee essentially performs the role of a conventional coupling, after installation of which it will be necessary to weld the junction.
However, there is an easier way, when welding is optional. In this case it is necessary:
- cut the pipe
- cut threads with a tap;
- connect a fitting with the required number of taps to the system.
Currently, it is the described technology that is considered the most preferable, no one wants to create "chaos" in their home, which will certainly arise if a welding machine is used.
If desired, the above technique can also be used for tapping into plastic pipes. But then, instead of one pipe, you need to take two small pipe structures and place a pipe segment equipped with a branch pipe between them. Such a pipe just makes it possible to connect additional equipment to the old sewer system.
2
If you do not like the tapping method, which involves cutting the pipe and removing some of it, you can try another technology. For example, prepare in advance a piece of tube with a nozzle having a specific size and section. After that, make a hole in the pipe, where it is planned to embed an additional structure. The hole in its cross section, as you yourself understand, must be identical to the hole on the previously prepared pipe.
Then you need to lubricate the surface of the flange to be attached, as well as the surface around the hole, with sealant, attach the pipe and flange to each other. To increase the reliability of the resulting connection, it is desirable to use clamps. They are tightened until the sealing compound appears on the surface of the joint. It should be removed immediately. In situations where there is a small pressure of water (drainage) in the system, it is allowed to use ordinary electrical tape instead of more expensive clamps.
Also, tie-in into the pipe can be carried out using a special adapter with a cross section of 5 centimeters, which is designed for installation on tubular products with a diameter of 10–11 centimeters. The procedure is as follows:
- access to the sewer pipe is blocked;
- calculate the distance of the pipe from the installed tie-in;
- a crown of the required diameter is prepared, which is mounted on an electric drill and a hole is made in the pipe.
Further, if an adapter is used with bolts, they must be tightened. If no bolts are provided, the tie-in is applied to a well-degreased surface and the nut is carefully tightened. In this case, it is also recommended to additionally treat the junction of the structure with the adapter with a sealing compound, which will give a 100% guarantee that the pipeline will not leak during its operation.
Recently, in addition, tie-ins with plastic fittings have often been used. They are designed for installation on pipes with a cross section of 32 to 40 mm. Such tie-in options have a diameter of 19 to 22 mm. The essence of their installation is similar to the processes described above.
3
As you know, in the past, almost all domestic sewer pipes were made exclusively from cast iron. There were many reasons for this, we do not plan to discuss them here, a lot has been said about the merits.
Today, more and more often, old cast iron systems are being replaced with more modern plastic ones. At the same time, in many apartments, the sewerage system is made of cast-iron pipes. And it is in them that it is often necessary to embed new branches in order to connect one or another household appliance that requires the supply and removal of water.
All of the previously described tapping methods are suitable for cast iron structures. You can use a ready-made tee or flange, or make the latter yourself according to the following scheme:
- a pipe section is taken with such a cross section (internal) that is similar to the cross section (now external) of the tubular product to which it is planned to connect;
- cut the pipe in the longitudinal direction, make a hole of the appropriate section in it and connect the branch pipe (weld this element).
Here we immediately note that welding work should be carried out extremely responsibly, so that subsequently tie-in into a cast-iron pipe of a water supply or sewerage system does not turn into serious problems. In some cases, as we have already said, sealant and special clamps are used instead of welding. But only when the flow pressure in the engineering system is minimal.