In modern high-rise buildings, the sewer system is made of polypropylene pipes, which have a lot of advantages. Cast iron risers are still quite common in the buildings of the old foundation. Many of them have long lost their original appearance and require replacement.
If you decide to upgrade the sewer system, but your neighbors do not plan repairs in the near future, you will have to make the transition from cast iron to plastic. Such a connection is made in several ways, each of them has its own nuances. Read more about this and the whole process of repairing sewers in our article.
What difficulties can be encountered in the process of work?
The most difficult stage in all sewerage repairs is the dismantling of the cast-iron pipe. Over time, all joints look like a whole, which greatly complicates their caulking.
When switching from cast iron to plastic, it should be noted that the standard polypropylene pipe is a bit narrower than its metal counterpart, which is why there is a gap in the slab.
The difficulty of dismantling lies in the fact that in Soviet times, pipes were connected using cement mortar and sulfur. After many years, this fixation becomes much more reliable and stronger.
Cement compounds have to be knocked out. To weaken the sulfur compound, the craftsmen use a gas burner. As a result of its operation, rather unpleasant odors are released into the air, which necessitates the use of protective masks.
If the neighbors still have the old sewage system, they need to carefully knock out their pipe, since cast iron is subject to cracking. Any unsuccessful blow can lead to the fact that the neighbors will have to change the riser.
Preparation for work
When planning to replace a pipe, specify the dates and the date of work with neighbors. Ask them not to use the sewage system during this period, but rather, block the water throughout the riser.
To deliver as little inconvenience as possible to the residents of the house, prepare the necessary tool in advance. This list includes:
- a grinder with a disc for metal (or a pipe cutter);
- scrap;
- chisel;
- hammer;
- screwdriver;
- grinding machine (or just paper);
- nail clipper;
- drill or punch.
Equipping the sewer transition from cast iron to plastic, cover the floor and plumbing with plastic wrap. Prepare old work clothes, gloves, face shield. Find a place in advance in the apartment where you will put old sewage elements.
Procurement of materials
Going to buy new pipes, pay attention to the diameter of the old riser. The standard parameters of the transition from cast iron to plastic are 110 mm, however, thicker options are also found.
If you want to reduce the size of your sewer pipe, you will need special rubber couplings, with which the transition is carried out. In cases where the pipe is absolutely flat (without a special flange), a plastic sleeve is used. It allows you to make a different transition from cast iron to plastic (160 to 110; 180 to 110; 110 to 100; 110 to 50 mm).
Also for work you will need:
- plastic pipe of the corresponding diameter;
- fasteners for fixing a new pipe to the wall;
- compensation pipe, by means of which a transition between two pipes is arranged.
- plumbing sealant;
- tee with pipe bends;
- level;
- FUM tape.
Also purchase a bottle of detergent or liquid soap. Soap solution is useful to you in the process of joining new sewage elements.
Dismantling process
The dismantling of the pipe should be carried out in such a way as to prevent the destruction of parts of the pipes located in the ceilings between floors, since in these places the transition from cast iron to plastic will be carried out.
The removal of the old pipe is carried out in the following sequence:
- Disconnecting pipes from the riser.
- Dismantling small sections of sewers.
- Making an upper cut on the pipe. To cut the pipe, you need to deviate from the ceiling about 10 cm.
- Making an incision from the bottom of the pipe. File should be indented 80 cm from the tee.
When you cut the pipe, wrap the upper edge of the sewage system with a film, since liquid can drip from there during work. Next, using a puncher, grinder, hammer and crowbar, disassemble the lower tee with bends and fittings.
If the seams between the pipes are almost invisible, embroider all the joints with a metal sheet. When the old pipes are removed, grind the metal edges of the upper and lower pipes with a grinder. Next, join the pipes in one of the following ways.
Transition with rubber pad
If a flat socket is located at the place where the pipes are joined, it is possible to transfer cast iron to plastic with a sleeve (110 mm). With this connection, the polypropylene pipe is inserted into the cast iron, deepens in it by 30-80 mm.
This method is considered simpler, but the service life of such a system does not exceed 8 years.
The work is carried out as follows:
- The bell is cleaned of rust, dust and dirt.
- The outside of the rubber cuff is covered with plumbing sealant.
- An adapter made of rubber is installed inside the cast-iron bell;
- A new pipe is installed in the cuff.
If there is no bell in the pipe, installation in this way can be done using a plastic adapter.
Docking using linen winding
A sufficiently reliable and popular method of joining pipes is considered to be caulking using natural reeling. This method can be used in cases where there is no special sealant at hand.
The transition from cast iron to plastic is arranged as follows:
- In a plastic pipe (in the area of its junction with cast iron), wrap several layers of plumbing.
- Insert the pipe into the cast-iron end of the riser protruding from the ceiling, using a narrow spatula, push the winding into the space between the two pipes.
- For greater reliability, the junction can be treated with a reinforcing composition. It is made from a mixture of cement, water and ordinary PVA glue.
The question of the durability of this docking method raises different opinions of specialists. Someone safely uses it in everyday work, while someone claims that with such a fixation, periodic leaks cannot be avoided.
In any case, if you decide to use this particular method, pay attention to the fact that it will be possible to use the sewage system only in a day, when the cement mortar is sufficiently hardened.
Combination connection
If you want to improve the reliability of pipe joints and make a high-quality transition of sewage from plastic to cast iron, use several methods at the same time.
For example, if there is a large gap between the cast iron and plastic pipe, you should use standard caulking and supplement it with a rubber cuff.
If you leave the lower tee intact, you will have to connect the toilet to the cast-iron pipe. To do this, the sewer corrugation can be inserted into a rubber cuff and additionally treated with a silicone joint or filled with a linen winding.
The sewer lines entering the riser will have to be docked in a similar way. They are mounted using a special plastic adapter and a 50 mm cuff.
If you understand the question of which is better: linen winding or silicone, it should be noted that flax is used only if there are large gaps at the junction. If the seam does not exceed 2 mm in width, it is best to use silicone.
Docking using special press fittings
It will facilitate the work on arranging the transition from cast iron to plastic cuffs and special adapters created for joining plastic and metal risers. Their peculiarity lies in the fact that one side of such an adapter has a thread, and the other a socket designed to fix the plastic sleeve.
This fixation is considered the most reliable, but also time-consuming. The work is carried out in the following sequence:
- The end of the cast-iron pipe is cleaned and a thread is cut into it (5 cm deep).
- An FUM tape or linen winding is wound around the fitting thread. Also for this purpose, you can use special plumbing paste-like compounds.
- Hand tighten the adapter to the pipe. Do not tighten strongly immediately.
- A plastic pipe is inserted at the other end of the sleeve onto which the pressure sleeve is attached.
When the pipe is installed, the cuff is crimped using a hand press. The plumbing nut tightens the nut on the fitting thread.
Tips for arranging a new sewer riser
When arranging a plastic riser in your apartment, pay attention to the fact that such pipes are characterized by low noise insulation properties. To ensure that the installed system produces less noise, securely fasten the pipe with special clamps with rubber gaskets. Pull the riser to the nearest wall to avoid additional vibrations.
If you want to ensure absolute silence in the bathroom, sew the pipes with a GVL box, but pre-fill the free space with mineral wool.
Often, in order to reduce noise, homeowners use machine noise isolation. It is convenient in that it has one adhesive side, due to which the pipe can be coated with it without much difficulty.
To summarize
In the process of repairing the sewage system: switching from cast iron to plastic (100 mm and wider joints) - strictly follow the technology for such work. When using threaded press fittings, be sure to treat the joining points with additional materials, since such seams are more prone to leakage.
If you have chosen the option of arranging the joint using adapter couplings, do not forget to cover the rubber element with a layer of sealant. Direct connections of sewer pipes are equipped with tight rubber gaskets. So that the elements of the system fit well into each other, pre-coat them with soap and water.