In recent decades, the monopoly of old cast iron pipes, installed almost everywhere in old sewer systems, has been noticeably squeezed out by modern plastic analogues.
And we must admit: plastic pipes and fittings have already shown themselves to be excellent in practice - they are durable and have good permeability (if anyone doubts). In any case, if you still use cast iron pipes in your old house or apartment, you should be prepared that sooner or later you will have to replace them with plastic ones. And if there is no talk of completely replacing cast iron yet (it’s not so easy to change an entire riser in a high-rise building), then anyone can easily connect the pipes together with a reliable joint. And this is not so difficult, in principle anyone can do it, but you still need to know the nuances in order to do it correctly.
As a matter of fact, it is precisely these very nuances of how to connect a plastic sewer pipe with a cast iron one, well known to experienced specialists, that usually constitute main problem for newbies.
So, if you are interested in this issue, most likely you have a cast iron riser or some other piece of pipe that needs to be properly connected to a plastic one.
The quality of the connection must be such as to eliminate the risk of leakage at the joint. Considering that it is usually advisable to complete such work in one day, it becomes clear that one must be well prepared for this “operation.”
Important: When removing old cast iron pipes, do not forget that they are extremely fragile. Do not use a regular metal hammer for this work, use a rubber or wooden one. In former times, joints on the sockets of cast iron products were sealed, as a rule, using cement mortar or with rags, having previously soaked them with paint. Admittedly, such a connection is quite strong, so carefully pull the pipe out of the socket, gently turning it from side to side.
What to do if the bell is damaged? You can't leave him in this state. Using a grinder, you need to carefully cut off the section of pipe up to the socket. Then the junction of the plastic pipe with the cast iron pipe can be joined more efficiently. Clean the cut piece of pipe thoroughly, removing dirt and rust, only then can you begin the joining process itself. You can cut metal with a hacksaw, but it will be tedious and time-consuming.
Important: Do not break off the sawn section of the cast iron pipe. Due to the fragility of the material, the product will almost certainly break somewhere nearby, and you will need to cut it again.
Methods for connecting a cast iron pipe to a plastic one
In cases where the old cast iron pipe must be removed, and inner surface the bell of the remaining pipe is smooth, you can get by in a simple way connections using any of the special plumbing seals.
Simple docking can be done in three ways:
- using a rubber gasket. The plastic pipe is inserted into the cast iron pipe by 3-8 8 cm. The connection can be made quickly and immediately after this the sewer system is in operation. This connection will normally last up to 6-8 years.
- caulk with linen wrap. This method is traditionally used for joining cast iron pipes, but it is also good for mixed joining. 1) in the area of the junction on plastic pipe Plumbing winding is wound in layers. 2) the winding is pushed into the gap between the pipes with a spatula or screwdriver (this is called chasing); 3) transition to cast iron pipe treat well with a solution of water, cement and PVA glue. It is not advisable to use the sewer for at least a day.
- seal with silicone. The method is good when there is a small gap (up to 2 mm) at the junction of the pipes. When carrying out work, pay attention to the tightness of the joint below. 1) thoroughly dry the joint; a hair dryer will help speed things up; 2) silicone is driven into the gap between the pipes with a construction gun, and the deeper, the more reliable. 3) the silicone must be allowed to dry, this is at least 3-5 hours.
With a creative approach, these options can be combined. If the gap between the pipes is large, use rubber gaskets along with caulking. In case of connecting the toilet with a button accordion ( corrugated pipe) use caulking with linen winding, covering the joint with sanitary silicone. It is also used to coat cast iron crosspieces and rubber seals.
It is important to understand that the junction of a cast iron pipe with a plastic one will only serve reliably if it is not subjected to damage during the installation process. various kinds mechanical stress and temperature changes. After all, this is what it is main reason leakage – the tightness is broken due to the fact that cast iron and plastic have different coefficients of thermal expansion.
If we are talking about sewer pipes through which flows do not pass hot water, this condition is not difficult to meet.
It happens that apartment owners do not resort to adapters at all - a plastic pipe is simply inserted into a cast-iron socket sealed with cement. As a result of this, it is deformed, and the cement from the hot water is full of cracks. So the joint loses its tightness.
Advice: in extreme situations, you can seal the junction of plastic and cast iron pipes with porous rubber, carefully wrapping it around the plastic pipe, and then drowning the remains in the socket.
In practice, the connection of cast iron pipes and plastic ones can be done in several ways, depending on whether the cast iron pipe has a socket or not. If there is a socket, even an untrained person can make the joint. If the bell is missing or damaged, you will have to show skill and tinker. Fitting connections are used successfully. To do this, take a press fitting with a thread for cast iron at one end, and a socket for plastic at the other.
Before you start work, prepare a special rubber adapter, which is designed for installation in a cast iron socket; you can easily buy one in any plumbing department. Sewer pipes, as a rule, have the same diameters; you can hardly go wrong. You will need an adapter with a diameter 5 cm or 11 cm. However, there are pipes of other diameters, then you will have to determine its value yourself.
The docking process is simple. The bell is cleaned of rust, dirt and moisture. It is advisable to coat it with sealant. The rubber adapter is also lubricated with any sealant, for example, silicone, and then recessed into the cast iron socket. Attention must be paid to ensuring that it is completely recessed in the socket, i.e. reached the limit.
The end of a plastic pipe is inserted into the adapter - the result is a reliable and easy-to-make connection, easily dismantled if necessary (clean, check), then returned to its place.
Attention! The plastic pipe entering the cast iron socket must necessarily have a slope towards the riser.
Connection of pipes with socket
In this case, we will need smooth edges of the pipe. The transition from a cast iron pipe to a plastic one is carried out in two stages. After cleaning the surface of the pipe, a special rubber adapter is put on it, pre-coated inside with sealant. A plastic adapter is put on top of it. The plastic waste pipe is inserted into the plastic adapter. This connection is also removable. Before purchasing adapters, make sure that their diameters correspond to the required ones.
Tip: if a loose connection is detected, it is recommended to use silicone sealant, which can be used to fill existing cracks.
Fitting connection
For it you will need a pipe cutter, which we will use to cut threads on a cast iron pipe. It is assumed that the bell is missing. If the metal already has a thread, the joining process is greatly simplified. If there is no thread, then it must be cut. To do this, lubricant is applied to the pipe, after which the thread we need is cut with a pipe cutter.
FUM tape or ordinary tow is wound onto the finished thread, after which a press fitting is screwed onto it. You need to screw the fitting on by hand, without using a wrench. The fact is that wrench It's very easy to overtighten the connection. As a result, the fitting or pipe may be damaged. It will be possible to eliminate a possible leak a little later, after the water is turned on.
As you can see, the process of replacing pipes, as well as joining them together, can be done independently. The most important thing is to work carefully and patiently, adhering to the work technology.
Correct caulking of the fan tee. Dismantling of cast iron sewer. Transition from cast iron to plastic (video)
Replacing a cast iron pipe with a plastic one for a toilet (video)
Sewer pipe socket
Plumbing. How to connect two pipes without a coupling and neck. Experiment
Replacing a cast iron pipe with plastic in the kitchen
If the main element that will make up your new sewer system is a plastic pipe, the cast iron pipe must be removed. Or at least reduce it as much as possible.
Why change
Soviet plumbing was simple and monotonous. A tiny toilet with a cast-iron riser in the corner, next to the bathroom, another riser in the kitchen - that’s all. But times change, new ideas in planning appear, new plumbing and new requirements for it.
All currently produced plumbing fixtures are unified and adapted for connecting plastic pipes to them. Their design does not provide for the use of cast iron sewer pipes. Plastic has many advantages. It is much lighter than cast iron, easy to install and much more economical than steel or cast iron pipes.
Plastic pipes are sold in various lengths, with ready-made branches and corners. Each of them has a socket for a tight and reliable fit of one pipe into another. All this allows you to assemble the entire sewer system in just a few minutes. Thanks to this simplicity, it is possible to install other plumbing fixtures, slightly changing its location. But there is one problem that cannot be avoided. Through all multi-storey building A common cast iron riser is installed from bottom to top. And there is a need to make a transition from cast iron to plastic.
How to go
How to connect a cast iron sewer pipe to a plastic one, while ensuring the reliability of the connection? There are several ways to do this.
The simplest is the connection through a rubber adapter. The size of the pipes is standard, and therefore this transition provides that a plastic pipe will be tightly inserted into it, and it will fit hermetically into the cast iron one. Connect your sewer system to the common one in this way quickly and reliably. Unfortunately, it is not always possible to do this.
It is possible to connect a cast iron pipe with a plastic one using one adapter only when it is seat is in perfect condition, smooth, has no cracks or chips.
But this does not always happen. Pipe joints burst over time and become covered with cracks.
Embossing using winding
It may happen that the diameters of the joined pipes do not fit each other or the condition of the inner surface of the cast iron pipe socket does not allow the use similar method. In this case, they use the good old method of “chasing”, which was previously used to connect cast iron pipes. To do this, you will need plumbing linen winding.
The joints are prepared as follows: the cast iron pipe is thoroughly cleaned inner part, and the end of the plastic one is wrapped in several layers of winding. Then we insert one pipe into the other. What you end up with is a weak and unreliable connection.
It needs to be compacted. The winding is rolled up into a kind of bundle or rope, which is pushed in a circle with a thin spatula into the gap between the pipes. The joints are driven to approximately 2/3 of the depth, and care should be taken to ensure maximum packing density. The remaining space is filled with a mixture consisting of cement, glue and water.
Difference from old methods
In Soviet times, before connecting a cast iron pipe, they heated the sulfur mass and filled the cracks with it. But this is very dangerous to health, so more civilized methods are now used.
It will not be possible to connect the resulting connection to work immediately; you will have to wait for the cement to harden, but the joint made using this technology is strong, reliable and simple.
Very often, nowadays, to solve the question of how to connect a plastic pipe to a cast iron one, they do not even use winding. Construction stores are replete with various types of sealants. This is silicone, which qualitatively fills the free space of the joint, firmly adhering to the walls. At the same time, it does not harden completely, remaining moderately plastic. Thanks to this, the joint is insensitive to vibration and minor bending loads.
Connect pipes from different materials Maybe. Sometimes this is done quickly, sometimes you have to tinker, but this work is quite within the capabilities of any skilled owner. Therefore, if you have new ideas for placing plumbing fixtures, then you should not be stopped by the lack of a sewer outlet near your chosen location. This is a solvable problem. You simply make the transition from cast iron to plastic and make the wiring you need.
When connecting water or sewer pipes, such a problem often arises as connecting a modern plastic pipe to a cast iron one. This must be done whenever new plumbing is installed in a home with old plumbing fixtures.
Basic methods
There are the following methods for connecting cast iron sewer pipes to plastic ones:
- flanged;
- fitting;
- using rubber gaskets;
- pressing tow or sanitary flax.
Optimal for home conditions is connection using fittings, various couplings or rubber adapter gaskets. A flange connection is used if the diameter is from 50 mm.
Application of fitting
From a technical point of view, optimal solution- this is the use of a fitting, a special adapter made of durable polyvinyl chloride. It has a thread on one end and a socket for inserting a plastic pipe on the other. Fittings are used if the cast iron pipe does not have a socket at the end, or its use is impossible.
You will need a die for cutting external threads, a fitting of a suitable caliber, FUM tape or plumbing flax or tow. It is necessary to cut off the cast iron socket with a metal grinder or a hacksaw. During this, you need to make sure that the cast iron does not crack.
It is necessary to clean the cast iron from dirt and paint and cut a 3-5 cm thread on it. Re-clean it from dust and metal residues and wind several turns of FUM tape or flax to seal the thread and screw the fitting.
After this, all that remains is to insert the end of the water pipe or sewer pipe into the fitting collar.
If a cast fitting without thread is used, then first an O-ring is placed in the socket, securing it with special glue, and then a narrow fitting pipe is inserted into it.
Press fitting for connecting metal and plastic pipes
Rubber gaskets
It is possible to simplify installation with the help of rubber gaskets, if the cast iron part is well preserved, its edges and inner surface are smooth, not rusted and without chips. As a rule, the sockets of strong and thick sewer pipes remain in this state.
The bell is pre-cleaned from dirt and rust.
A rubber adapter gasket of a suitable caliber must be well coated with silicone sealant. Insert into the connection until it stops, but not less than 3 cm. After this, insert the pipe of the connected water supply into the cuff. The work is finished.
Linen winding
Press-fitting with linen winding is used if other connection methods are not available, or as a temporary measure. Several layers of plumbing flax or tow are tightly wound onto the plastic pipe at the junction. It is inserted into the sewer connection, the flax is pressed into the gap with a knife or spatula and sealed with silicone sealant or a mixture of cement and PVA glue. All you have to do is wait a day, and you can use the connection.
This connection of sewer pipes can be used for a limited time (up to a year) until it becomes possible to install a more reliable structure.
Preparatory work
In addition to modern water pipelines with a diameter of 50 or 110 mm (depending on the purpose - replacing a riser or a sewer section), you will need:
- metal saw;
- mallet or hammer with a rubber striking part;
- spatulas;
- flax, FUM tape;
- adapters for the selected method.
You need to separate or saw off the worn part of the old cast iron system using a mallet. A metal hammer can crack cast iron, which creates a problematic situation when repairing sewer drains. After disconnecting, you need to clean out the remnants of the old sealant (this could be cement) and flax, clean the cast iron from rust and dirt, degrease and, if necessary, cut threads on it.
Features of flange connection
It is used if the diameter is 110 mm or more in the sewer pipeline. A flange is a metal disk with holes for bolts and a wide ring with which it fits onto the part being fastened. It is used on both the cast iron and plastic sides.
The flange is welded to the cast iron pipe (drain). When the metal has cooled, a rubber sealing gasket and a crimp coupling are put on the plastic structural element. After this, the coupling is moved to the end and attached to the flange bolted connection. For reliability, an O-ring is placed between the flanges.
Sealing joints
Gaps up to 2 mm wide can be sealed with silicone. This method is used for temporary repair of a sewer or other system, or during installation using flax pressing.
The joint must be perfectly dry. It is recommended to use a hair dryer for drying. The gap is filled with silicone as deeply as possible using a construction gun, the joints are moved, closing the gap (if possible), and coated with sealant on top.
The system can be used after 5–6 hours.
Method 1. Rubber gasket
If the old cast iron pipe can be easily removed, and the inner surface of the collar (bell) of the remaining cast iron pipe is smooth, then a simple joining method using a special sealant will do. 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 continue operation immediately after that sewer system. Practice shows that such a connection of plastic and cast iron pipes can function normally for 8 years.
Most often sewer riser there are 2 outlets, and the first has a diameter of 100 - for connecting a toilet, and the second - 50 - for connecting a drainage system that provides output apartment sewerage. In both cases, the connection is made using the same technology. Necessary:
- clean the bell from rust and dirt;
- apply to the rubber transition with outside sealant cuffs;
- insert the rubber adapter into the cast iron socket;
- insert a new sewer pipe into the cuff.
If the connection has to be made with a pipe that does not have a socket, then you will have to use a plastic adapter. In this case, do this:
- a part of the cast iron pipe is cut off with a grinder, leveling the edge;
- a rubber adapter is put on this part;
- coat the edge of the “clad” cast iron pipe with sealant;
- A plastic adapter (cuff) lubricated with sealant is also placed on top of the pipe.
Appearance and application diagram of the plastic adapter: 1 - plastic socket; 2 - rubber ring; 3 - plastic adapter; 4 — rubber cuff; 5 - second rubber ring; 6 - cast iron pipe without socket.
The cuffs and transitions must be of the appropriate size for the pipes. The connection of cast iron and plastic pipes using the transition technology is the same for all diameters.
Method 2. Caulking with plumbing linen winding
Typically, this method is used when joining cast iron pipes, however, it is also well suited for mixed joining. When performing work in accordance with this method, perform the following actions:
- in the area of the joint, plumbing winding is wound onto the plastic pipe in several layers;
- using a narrow spatula or a wide screwdriver, the winding is firmly pushed into the gap that exists between the two pipes (this is what it is);
- the transition to a cast iron pipe is coated several times with a polymer-cement solution, which contains water, cement and PVA glue;
- After completing the work, it is not advisable to use the sewer system for at least the first 24 hours.
The joint made in this way is quite reliable. This method was widely used before it became commercially available. silicone sealants However, even today it is often used when connecting a plastic pipe to a cast iron pipe under a sink or washbasin. Even several years after joining pipes in this way, if they occur, then, as a rule, not at the junction of the pipes.
Method 3. Sealing with plumbing silicone
If the connection of a plastic pipe to a cast iron pipe is accompanied by the formation of a small 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, you must:
- Before joining, the joint area is thoroughly dried; it is advisable to use a hair dryer;
- use a construction gun to push silicone into the gap between the pipes, taking into account that the deeper the silicone penetrates, the more reliable the connection between the cast iron pipe and the plastic pipe will be,
- The silicone layer needs to dry - usually complete drying occurs within 3-5 hours, while a thicker layer takes longer to dry.
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, use rubber gaskets along with caulking. So, when connecting a toilet with a “bayan”, that is, a corrugated pipe, caulking is used with linen winding, followed by covering the joint with sanitary silicone. At the same time, the cast-iron crosspiece at the joint and the rubber seals are coated with sanitary silicone.
- When caulking, silicone is often used instead of a polymer cement solution.
Connection using a press fitting
If you use a press fitting (an adapter for cast iron pipes with a thread for a cast iron pipe at one end and a socket for sliding connections of plastic pipes at the other), use tow or Teflon tape.
Technology for performing work using a press fitting:
- cut off old pipe using a grinder or unscrewing the coupling on a cast iron pipeline at the future junction with a plastic pipe;
- the edge of the pipe is lubricated with oil or grease until it exits the die;
- use a thread cutter to cut a thread, wipe it and wrap tow or FUM tape on it;
- lubricate the winding with silicone;
- The press fitting is screwed onto the thread by hand (a wrench is not used so that the press fitting does not crack); it can be tightened 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 must 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 detachable brass couplings with a PVC element, or transition couplings equipped with a rubber seal.
In conclusion, it should be noted that following the rules mandatory when connecting plastic and metal pipes, it is possible to carry out high-quality work both in case of repairs and during the planned replacement of cast iron pipes with plastic ones.
When replacing old sewer, it may be necessary to connect a plastic pipe to a cast iron pipe. It is advisable that such work be carried out by specialists, but if you wish, you can do everything yourself.
To prevent leaks or blockages from occurring after replacing the pipeline, it is necessary to properly connect the plastic pipes to the cast iron. In this article we will figure out how to properly connect a cast iron pipe to 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 the section coming from the toilet -. In addition, you will also have to purchase a certain number of adapters, angles and other fittings.
Before starting work, prepare the material and tools:
- plastic pipe of the required diameter;
- a coupling that will be used to make the transition from cast iron to plastic;
- wooden or rubber mallet;
- grinder or hacksaw for metal.
It is advisable to complete the replacement of the sewer pipeline within 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 there is a socket for connecting a plastic pipe. You will also need Teflon tape (FUM tape) or plumbing 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 thread, if necessary, on the cut area.
- We clean the threads from dust and wrap tape or flax around it, lubricate it with silicone grease.
- We screw on the press fitting.
Advice!
Screw on the press fitting by hand, without a key, as it may crack with strong force. You can tighten it after turning on the water.
You can also connect a cast iron pipe to a plastic one using a cast fitting. For this:
- Degrease the joint area.
- We treat the joint with plastic glue and sprinkle it with sand, wait for the glue to dry completely.
- Clean the bell and degrease it.
- We treat with sealant.
- We install the sealing ring.
- We 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 it and its edges and the inner surface remain smooth. The pipe should extend into the socket by an average of 5 cm. With this connection method, the sewer can be used immediately after all work is completed. Installation steps:
- we clean parts from rust, dirt, etc.;
- Coat the rubber adapter with sealant on the outside.
- insert the rubber adapter into the cast iron socket;
- insert the pipe into the cuff.
If pipes that do not have a socket are connected, then a plastic adapter is used. Then proceed as follows:
- cut off a piece, align the edges;
- put on the rubber adapter;
- coat the edge with sealant;
- We put a plastic adapter lubricated with sealant on top.
Silicone sealing
The gap formed when connecting the pipes (up to 2 mm) can be sealed with plumbing silicone. This method is quite effective if Special attention apply to the bottom of the joint.
- Dry the joint area using a hair dryer.
- We fill the gap with silicone as deeply as possible, for this we use a special construction glue gun.
- We wait until the silicone dries, usually this happens in 3 - 5 hours.
Socket connection
For this type of connection, you need to buy a special adapter that is designed for installation in the socket. This item can be purchased at any hardware store, products with a diameter of 50 or 110 mm are usually required. But there are pipes of other diameters, so it’s better to decide in advance.
The connection process takes place in several stages:
- we clean all connected parts from dirt, dust and other things;
- coat them with sealant;
- We insert the adapter all the way into the cast iron socket;
- 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 pipe adjacent to the main pipe.
- We weld the metal flange part.
- Place the crimp sleeve on the workpiece.
- We connect the flanged parts, placing an O-ring between them, with bolts.
It is possible to carry out high-quality work in the event of repairs or planned replacement of cast iron pipes with plastic ones only by following the installation steps. I would also like to note that it is better to carry out this work in advance, rather than wait for an accident.
Video: transition from cast iron to plastic pipes, nuances and tricks in replacing plumbing fixtures, pvc pipes and sewerage
