How to connect a plastic pipe to a cast iron pipe. How to connect a cast iron sewer pipe with a plastic one - fittings, transitions, other connection options Connecting a plastic pipe to a cast iron sewer

Method 1. Rubber pad

If the old cast iron pipe can be easily removed, and the inner surface of the collar (socket) of the remaining cast iron pipe is flat, then a simple method of joining using a special seal is suitable. In this case, the plastic pipe is inserted into the cast iron pipe by 3, and if possible, by 8 cm. This method allows you to make the connection quickly and immediately after that continue the operation of the sewer system. Practice shows that such a connection of plastic and cast iron pipes can function normally for 8 years.

Most often at sewer riser there are 2 outlets, the first one having a diameter of 100 - for connecting a toilet bowl, and the second - 50 - for connecting a drain, providing an outlet apartment sewerage... In both cases, the connection is performed using the same technology. Necessary:

clean the socket from rust and dirt;
apply to rubber transition with outside cuff sealant;
insert the rubber adapter into the cast iron bell;
insert a new one into the cuff sewer pipe.

If the connection has to be made with a pipe that does not have a socket, then a plastic adapter will have to be used. In this case, proceed as follows:

part cast iron pipe cut off with a grinder, leveling the edge;
a rubber adapter is put on this part;
coat the edge of the "dressed" cast-iron pipe with a sealant;
on top of the pipe, a plastic adapter (cuff) lubricated with sealant is also put on.

Appearance and application diagram of the plastic adapter: 1 - plastic bell; 2 - rubber ring; 3 - plastic adapter; 4 - rubber cuff; 5 - the second rubber ring; 6 - cast iron pipe without socket.

The collars and transitions must be of the correct size for the pipes. The connection of cast iron and plastic pipes using the transition technology is the same for all diameters.

Method 2. Stamping with flax plumbing

Usually this method is used for joining cast iron pipes, however, it is well suited for mixed joining. When performing work in accordance with this method, the following actions are performed:

in the area of the joint, a plumbing roll is wound on a plastic pipe in several layers;
rewinding with a narrow spatula or wide screwdriver is firmly pushed into the gap that exists between the two pipes (this is);
the transition to a cast-iron pipe is coated several times with a polymer-cement mortar, which includes water, cement and PVA glue;
after completing the work, it is undesirable to use the sewer for at least the first 24 hours.

The joint made in this way is quite reliable. This method was widely used before the commercialization of silicone sealants, however, and is now often used when connecting plastic pipe to the cast iron under the sink or washbasin. Even several years after the pipes are joined in this way, if they do occur, then, as a rule, not at the pipe joint.

Method 3. Sealing with sanitary silicone

If the connection of a plastic pipe with a cast iron pipe is accompanied by the formation of a slight gap (no more than 2 mm), then this method turns out to be very effective. When carrying out work, special attention must be paid to ensuring the tightness of the joint in its lower part.

When performing docking in accordance with this method, it is necessary:

before joining, the joint is thoroughly dried, it is advisable to use construction hair dryer;
with a construction gun, silicone is driven into the gap between the pipes, while taking into account that the deeper the penetration of the silicone, the more reliable the connection of the cast-iron pipe with the plastic one,
the silicone layer must dry - usually complete drying occurs within 3-5 hours, while the thicker layer dries longer.

It is highly undesirable to use the sewer until the silicone dries.

Method 4. Combining the above methods

To increase the reliability of the joint between plastic and cast iron pipes, you can combine the above methods, for example:

If there is a large gap between the pipes at the junction, rubber gaskets are used along with capping. So, when the toilet is connected with a "button accordion", that is, with a corrugated pipe, a linen roll is used, followed by covering the junction with sanitary silicone. At the same time, the cast-iron cross at the joint and rubber seals are coated with sanitary silicone.
When capping, silicone is often used instead of polymer-cement mortar.

Press fitting connection

If a press fitting is used (an adapter for cast-iron pipes with a thread for a cast-iron pipe at one end and a socket for push-fit joints of plastic pipes on the other), use tow or Teflon tape.

Technology for performing work using a press fitting:

cut off the old pipe with a grinder or unscrew the coupling on the cast-iron pipeline at the place of the future joint with the plastic pipe;
the edge of the pipe is lubricated with oil or grease to the point where it comes out of the die;
cut the thread with a thread cutter, wipe it and wind tow or FUM tape on it;
grease the reel with silicone;
the press fitting is screwed onto the thread by hand (the wrench is not used so that the press fitting does not crack), it will be possible to tighten it after the water supply is turned on in case it is necessary to stop the resulting leak.

Important to remember:

The joining of cast iron and plastic pipes using a press fitting should be accompanied by taking into account the difference in the coefficients of thermal expansion of metal and plastic. For this reason, it is not recommended to screw PVC fittings onto metal.
During installation heating system or pipelines for hot water supply use split couplings made of brass with a PVC element, or transition couplings equipped with a sealing rubber.

In conclusion, it should be noted that following the rules that are mandatory when performing the connection of plastic and metal pipes, it is possible to perform work with high quality both in the case of repairs and with the planned replacement of cast iron pipes with plastic ones.

When replacing old sewer, it may be necessary to connect a plastic pipe with a cast iron one. It is desirable that such work be carried out by specialists, but if you wish, you can do everything yourself.

So that after replacing the pipeline there are no leaks or blockages, it is necessary to qualitatively connect the plastic pipes with cast iron. In this article, we will figure out how to properly connect a cast iron pipe with a plastic one.

All work can be divided into several stages:

preparation;
dismantling of cast iron pipes;
installation of plastic;
compound.

Preparatory work

The first step is to carefully measure the area to be replaced in order to know the number of pipes and what diameter you need to buy. Diameter is also an important aspect, for example, when replacing pipes with a diameter of 50 mm are used, and when or a section coming from the toilet bowl -. In addition, you will also have to purchase a certain number of adapters, corners and other fittings.

Before starting work, prepare the material and tool:

plastic pipe of the required diameter;
a coupling with which the transition from cast iron to plastic will be carried out;
wooden or rubber mallet;
grinder or hacksaw for metal.

It is advisable to have time to replace the sewer pipeline in 1 day.

Video: Installation of a transition from a cast-iron sewer pipe to a plastic one.

Removing cast iron pipes

The pipes are connected using press fittings. At one end of such a product there is a thread, and at the other end there is a socket for connecting a plastic pipe. You will also need Teflon tape (FUM tape) or sanitary flax for sealing and two adjustable wrenches.

Installation steps:

We unscrew the coupling or cut off a piece from the cast-iron pipe in the place where it will be carried out
connection with a plastic pipe.
We cut the threads, if necessary, in the cut off area.
We clean the threads from dust and wind tape or flax on it, lubricate with silicone grease.
We screw on the press fitting.

Advice!

Tighten the press fitting by hand, without a key, as it can crack with strong force. It will be possible to tighten it after turning on the water.

You can also connect a cast-iron pipe with a plastic one using a cast fitting. For this:

Degrease the joint.
We process the joint with plastic glue and sprinkle with sand, wait for the glue to dry completely.
We clean and degrease the bell.
We treat with a sealant.
We mount sealing ring.
Insert the narrow part of the fitting into the sealing ring.
We insert the edge of the plastic pipe into the fitting collar.

Connection with rubber gaskets

This method is suitable if you managed to remove the old pipe from both its edges and the inner surface remained even. The branch pipe should go into the socket on average by 5 cm. With this method of connection, it will be possible to use the sewage system immediately after the end of all work. Installation steps:

we clean the parts from rust, dirt, etc .;
We coat the rubber adapter with sealant from the outside.
insert the rubber adapter into the cast-iron bell;
insert the pipe into the cuff.

If pipes are connected without a socket, then a plastic adapter is used. Then proceed as follows:

cut off a piece, align the edges;
put on a rubber adapter;
coat the edge with sealant;
put on a plastic adapter greased with sealant from above.

Silicone sealing

The gap formed when connecting the pipes (up to 2 mm) can be sealed with sanitary silicone. This method is quite effective if you pay special attention to the bottom of the joint.

Dry the joint with a construction hair dryer.
We fill the gap with silicone, as deep as possible, for this we use a special construction glue gun.
We are waiting for the silicone to dry, usually in 3 - 5 hours.

Socket connection

For this type of connection, you need to buy a special adapter that is designed to be installed in a socket. Such a part can be purchased at any hardware store, usually products with a diameter of 50 or 110 mm are required. But there are pipes of a different diameter, so it is better to decide in advance with.

The connection process takes place in several stages:

we clean all the connected parts from dirt, dust and other things;
coat them with sealant;
insert the adapter, all the way, into the cast-iron bell;
insert a plastic pipe into the adapter.

This method is the simplest and most reliable, and if necessary, the connection can be disassembled and reassembled.

Flange connection

This method uses special connecting parts... In addition, the use of welding will be required, which does not always allow you to carry out the work yourself.

We clean the branch pipe adjacent to the main pipe.
We weld on the metal flange part.
We put the crimp sleeve on the workpiece.
We connect the flange parts by placing an O-ring between them with bolts.

It is possible to carry out quality work in the event of repair or planned replacement of cast iron pipes with plastic ones only by observing the installation steps. I would also like to note that it is better to carry out these works in advance, and not wait for an accident.

Video: transition from cast iron to plastic pipe, nuances and tricks in replacing plumbing, pvc pipes and sewerage

When it is necessary to replace cast-iron sewer pipes with plastic products, many homeowners are interested in how this work should be done. According to specialists, such a connection can be made using a press fitting or using one of four simple joining methods without it.

All of the above methods provide reliable repair pipeline.

Simple connection of cast iron and plastic sewer pipes

Method one - using a rubber gasket... If the old cast iron pipe can be removed without problems, and the inner surface of its socket (cuff) is even, then you can use in a simple way connections using a special seal. The plastic pipe must be inserted into the cast iron pipe by 3 centimeters, or better - by 8 centimeters.

In both cases, the connection is made using a single technology, for which:

first remove rust and dirt from the cuff;
a sealant is applied to the rubber transition located on the outside of the cuff (read also: "");
a rubber adapter is inserted into the cast-iron bell;
a new plastic tube is placed in the cuff.

In the event that the connection is made to a pipe without a socket, then you need to use a plastic adapter.

In this situation, proceed as follows:

part of the cast iron pipe is cut off with a grinder and the edge is leveled, after which a rubber adapter is put on it;
The "dressed" edge of the pipe is coated with a sealant;
on top of it is placed a plastic adapter, also treated with a sealant (read also: "").

The size of the collars and transitions must correspond to the diameter of the pipes used. The connection of cast-iron and plastic sewer pipes according to the transition technology does not differ for products different diameters.

In this case, the work is performed in the following sequence:

at the junction, a plumbing reel is wound on a plastic pipe in several layers;
using a wide screwdriver or a narrow spatula, push the reel tightly into the gap formed between the pipes (this is the work called stamping);
the place of transition to a cast-iron pipe is coated several times with a polymer-cement mortar consisting of water, PVA glue and cement;
after completion of the work, the sewage system should not be used for at least one day.

The joint, which is made in this way, is quite reliable and was used everywhere before the appearance on the domestic construction market silicone sealants, and now it is still used if you need to connect a plastic pipe to a cast iron pipe in the place under the sink or sink. Using high-quality sewer pipes and fittings, even after several years of using this method, no leaks occur at the junction.

Method three - sealing using sanitary silicone... When connecting a plastic pipe with a cast iron pipe, a slight gap may form, the dimensions of which do not exceed 2 millimeters. Then the replacement of sewer pipes from cast iron to plastic in this way turns out to be very effective (more: ""). Special attention when carrying out work, you need to pay attention to the tightness of the joint in its lowest part.

Docking in accordance with this method must be performed in the following sequence:

before connecting a cast-iron sewer pipe with a plastic one, the junction is thoroughly dried using a construction hair dryer;
the gap between the ends of the pipes is filled with silicone using a construction gun. The deeper the sealant penetrates, the stronger and more reliable the connection between the pipeline elements will be;
the silicone layer must dry well. As a rule, it takes about 3-5 hours to completely dry, depending on the thickness of the silicone applied. The junction can be coated with it both from the inside and from the outside, as in the photo. Do not use the sewer until the silicone dries.

Method four - a combination of the above three methods... In order to increase the reliability of the joint between plastic and cast iron pipes, it is permissible to combine the methods that were previously described in the article. For example: if available big slit between the pipes at the junction, capping and rubber gaskets can be used.

When connecting the toilet to sewer system with help corrugated pipe use linen coiling with a further overlapping of the joint with sanitary silicone. At the same time, the cast-iron cross and rubber seals located at the docking point are coated with the same material. When capping, the polymer-cement mortar can be replaced silicone sealant.

How to connect cast iron and plastic using a press fitting

Press fitting- this is a transition element for cast-iron pipes with threads for these products at one end, and on the other side there is a socket for sliding joints of plastic elements. When using it, you will need tow or Teflon tape.

Technological process pipe connections using pressfitting:

first of all, with the help of a grinder, they cut off the old pipe or unscrew the coupling on the pipeline in the place where there will be a joint with the plastic element;
lubricate the edge of the pipe with grease or oil to the point where it comes out of the die;
using a thread cutter, a thread is cut, then it is wiped and a FUM tape or tow is wound on it, smearing the winding with silicone;
then the press fitting is screwed onto the thread by hand. Tighten it after turning on the water supply, if a leak occurs at this point.

Before inserting a plastic sewer pipe into a cast iron pipe using a press fitting, you need to take into account the difference between the coefficients of thermal expansion of cast iron and plastic. For this reason, experts do not recommend screwing fittings made of polyvinyl chloride onto a metal base.

Observing all the rules for connecting plastic and metal pipes, you can do this work with high quality on your own, without inviting professionals.

There are several ways how to connect a plastic pipe to a cast iron sewer. Next, we will consider the main ones, features of their application, advantages and disadvantages, and the sequence of installation work.

1.Connection with fittings

This connection is necessary not only if necessary to connect cast iron installation with plastic, but even if there are problems in already installed system sewerage.

If you have a leak in the joint of a pipeline made of cast iron and plastic, then it was formed either due to a temperature drop or due to a water hammer. The latter are extremely rare. Temperature drops, however, happen often and are a common problem, as there are often disconnections and switching on. hot water... If such a problem occurs, the reason is a poor-quality fitting, the fastening of which has loosened and cracked. In order to fix this problem, replacing the connection with a crimp will help you. You will need to replace the old fitting with a new one.

You can also connect the sewer system using a press fitting, one end of which has a cast iron thread, the other - a special socket for connecting a plastic pipe. You will need two adjustable keys and a Teflon strap.

Unscrew the coupling from the cast iron pipe where there will be a connection to the plastic system, or cut off a piece of the old pipeline using a grinder.
Use grease to lubricate the edge of the nipple.
Remove dust from threads.
Cut the threads using a thread cutter.
Wipe the threads and wrap Teflon tape around them.
Lubricate the threads with silicone.
Screw the press fitting onto the threads. Be sure to use an adapter sleeve that has a special rubber seal, or use a split brass sleeve from plastic elements.

Tighten the press fitting by hand without a key in order to avoid breaking it.

Another method involves the use of a molded fitting.

Degrease the pipe joint using alcohol.
Treat it with plastic glue.
Sprinkle with sand.
Wait for the glue to dry completely.
Clean the socket from dirt, degrease.
Treat it with a sealant.
Fit the latex O-ring.
Place the narrow part of the fitting into the O-ring.
Insert edge plastic system into the fitting collar or corrugated adapter. Important: Avoid kinking the hose.

2.Rubber pad

Use a special seal - a rubber gasket - if you can easily dismantle the old cast iron system, the inner surface of the cuff of which is even. You will need to insert the plastic pipe 3-8 cm. The advantages of this method are that you can immediately use the sewerage system after connecting the pipeline, and it will function for about 8 years.

Clean any debris and rust from the sewer line.
Apply a coat of sealant to the rubber transition on the outside of the cuff.
Insert a special rubber adapter into the cast iron system.
Insert the plastic drain pipe into the collar.

Use a plastic adapter if there is no special socket in the pipe. Then you will have to cut off part of the cast-iron system with a grinder, put on an adapter made of rubber, coat the edge with sealant, put on an adapter made of plastic, which was previously lubricated with sealant.

3.Silicone sealing

If there is a slight gap in the joint, use a silicone seal at the bottom of the joint.

Dry the docking area with a hair dryer.
Fill the gap with silicone using a construction gun. Important: fill the gap with silicone as deep as possible.
Wait 5 hours for the silicone layer to dry.

4.Splared pipe connection

Prepare a special adapter made of rubber with a diameter of 5 or 11 cm, clean the flare from rust, coat it and the adapter with sealant. Place the socket all the way into the cast iron system. Next, insert the end of the plastic pipe into the adapter. The advantage of the method lies in its simplicity and reliability. Please note: when inserting the plastic pipe, it is important that it slopes towards the riser.

5.Flanged pipe connection

Dismantle the old system using a grinder. Strip the pipe that is adjacent to the main sewer system. Weld the metal flange to it. Slide a ferrule over the workpiece you previously machined. Connect the flange parts using bolts and nuts, placing a sealing ring between them. Tip: wire sewer installation in the direction from the riser.

V Lately when laying new sewage systems or repairing old ones, plastic pipes are very often used. Such products are characterized by light weight, anti-corrosion properties and long service life. In this article, we will tell you how to connect a cast-iron sewer pipe with a plastic one, if you need to carry out urgent repair sewerage systems.

One of the advantages of plastic pipes is their low tendency to clog. However, if the plastic pipes are not correctly joined to the cast iron pipes, the system may lose its tightness and leak, since the linear expansion rates for cast iron and plastic differ.

Preparatory stage

During renovation works with cast iron and plastic pipes, care should be taken, it is advisable to use rubber or wooden hammer... This is necessary so as not to accidentally split the brittle cast iron and cause clogging of the channel.

During the installation of plastic pipes, it is worth taking care of the presence of inspection hatches. They will allow in the future to diagnose the condition of the pipe in case of any malfunctions. Please note that for a 110 mm riser, it is optimal to use pipes with a diameter of 50 mm.

To connect sewer pipes from cast iron to plastic, you will need the following tools and consumables:

plastic pipe of the required standard size;
connecting elements;
adjustable wrench;
grinder or hacksaw for cutting pipes;
hammer with a wooden or rubber attachment.

Connecting elements can be all kinds of fittings, adapters, couplings, gaskets.

Common methods for joining pipes made of cast iron and plastic

You can choose a method of how to connect a cast-iron water pipe to a plastic one from the two most popular - flange or fitting connection. If it comes about the flange method, then two discs with holes are used, which are tightly pressed against each other with bolts, forming a joint. Often this method is used if the cross-section of the pipeline is large enough.

But when making the transition from a cast-iron sewer pipe to a plastic one, the cross-section of which does not exceed 110 mm, you can safely use fittings - at choice, crimped or cast. A molded fitting is a product that has a socket in which a sealing gasket has been pre-installed. But crimp fittings are prefabricated connections, and their installation is somewhat more complicated. They have a crimp ring that must have a cut. It will prevent a quick breakdown of the fitting and the occurrence of a leak in the sewer pipes.

Fittings are classified by type of installation as press fittings and compression products. Installation compression fittings somewhat simpler and faster, they allow you to create reliable connection... However, after some time after installation, the fasteners may loosen, leading to leaks and loss of tightness in the system.

An alternative is the use of press fittings. Such connecting elements provide a secure connection without any risk of leakage. Therefore, there is no need to perform subsequent monitoring of the state of the connections.

Among the types of fittings on the market, you can always find suitable products for sewer pipes.

Please note that the joining of cast iron and plastic sewer pipes can in no way be done with cement.

Rubber seal for connecting sewer pipes

In this way, you can dock pipes in cases where, after dismantling a defective section of a cast-iron pipe, a section remains without damage, chips and cracks, having a smooth socket and an expanded part at the end, or you can use an adapter for a cast-iron sewer pipe. In this case, a rubber cuff is first mounted, and then the plastic pipe deepens into the cast iron pipe at a distance of 5-8 cm.

Please note that before installing the sealing collar, the inner surface of the cast iron pipe is cleaned from dirt and rust. We can say that this way allows you to use the system immediately after the repair.

In some cases, the required expansion is not available on the remaining section of the cast iron pipe. Then you will need to use an adapter from a cast iron pipe to a plastic one. Before its installation, the cast-iron pipe must be cleaned, rust removed and the end part trimmed with a grinder. On the processed section, first put on a rubber gasket, and then a plastic insert in a cast iron pipe. After that, a piece of plastic pipe is mounted, and all seams are sealed with silicone.

Scope of application and advantages of press fittings

Press fittings can be used not only for connecting cast iron and plastic pipes, but also for eliminating problems in the finished sewer system. Please note that such products have a service life of about 50 years, and the acceptable pressure is up to 0.1 MPa.

First, a piece of a cast-iron pipe is cut off, without looking whether there is a socket on it or not. The resulting cut is cleaned with emery and a file so that the butt end is absolutely smooth, without burrs. Next, the outer surface of the pipe is lubricated with grease or mineral oil and a thread 3-5 cm long is cut on it, after which a plumbing thread is wound on it. Now you can simply screw the plastic fitting onto the pipe.

It is not necessary to exert significant force while screwing the fitting in order not to deform the cast iron. To avoid water hammer, it will be possible to finally press on the thread after starting the system.

A crimp collar is put on the plastic pipe and inserted on the other side of the fitting, after which the crimp is performed special tool... It is worth noting that the press fitting provides a very high-quality and durable connection, since a sealing rubber ring is installed on one side, and the threaded connection is sealed on the other.

Subtleties of mounting flange fasteners

As a rule, flanges are used for working with pipes of large cross-sections. If you need to dock the cast iron pipe flange with a smooth plastic product, you will have to use special adapters. The best choice to work with plastic products there will be loose flanges. When choosing a fastener, carefully check that there are no burrs or sharp edges on it that could ruin the plastic pipe.

When installing a flange mount, it is worth considering the following subtleties:

a stronger connection can be provided by a straight shoulder with a tapered transition;
for pipes with a cross section of more than 20 cm, you need to use a free flange resting on a conical collar;
for light pipes with a cross-section of up to 30 cm, as well as for heavy and medium-weight pipes polymer products with a section of up to 15 cm, free flanges are used, resting on a free shoulder.

The first step is to cut the pipe where they are going to establish the connection, making sure that the cut is perfectly even. A free flange with a rubber gasket is placed on the end, the overlap of which on the end should not exceed 1 cm. Next, the flange is pushed onto the seal and the connection is fastened with bolts. The bolts must be tightened evenly on all sides, and the allowable torque is indicated in the specifications.

The use of silicone for sealing joints

The method of connecting cast iron and plastic pipes is determined largely on the basis of their technical condition... For joints in an acceptable state, between the elements of which the distance does not exceed 2 mm, you can use sanitary silicone.

Remember that during the hardening of silicone, no mechanical impact on the joint is allowed.

The sequence of work is as follows:

a piece of cast iron pipe is first cleaned and dried;
on the plastic section the pipeline is wound with plumbing thread and deepened by 10 cm into the socket;
the remaining gap is filled with silicone, applying it under pressure with a pistol, so that a uniform and deep layer is obtained.

Silicone hardens within 3-5 hours, however, it is better to start the system a day after sealing.