Replacing pipes in an apartment: how to replace a sewer riser

Recommendation points

• Do I need a reason to replace a cast iron riser
• Preparing for the replacement and eliminating unpleasant embarrassment
• Dismantling work
• Transition fittings
• Restoration of a riser in plastic

Old cast iron sewer risers, perhaps, can be operated for more than a dozen years. But nevertheless, it is better to replace them so that in the future you will not experience difficulties with the distribution of drain pipes. We will tell you how to do it quickly and with the least loss..

Do I need a reason to replace a cast iron riser

There are many who like to dispute the necessity of replacing cast iron sewer pipes with plastic ones. They are guided mainly by the considerations that if the riser maintains sufficient clearance, its dismantling entails only a lot of dust and dirt, while not giving any tangible benefit.

The main snag here is this: cast-iron risers remained, as a rule, in the housing stock of Soviet-era buildings. During the construction at that time, the craftsmen did not pay attention to such issues as:

• tight abutment of the riser pipe to the wall;
• favorable location of the collector (cross);
• advantageously low level of the main drain hole (in particular, it is important for baths and shower trays);
• availability of all necessary technological units, for example, revision plugs.

It turns out that there are only two main prerequisites for replacing the riser. The first is the most compact placement of communications behind the false wall. Sometimes this is critical, because the risers usually pass through the toilet, which means that when they are hidden without installing the installation, the classic “knees resting on the door”.

The second prerequisite is the reliability of the drainage system during overhaul in the bathroom. Just imagine: you built a bathroom “pencil case” according to all the rules, spent money on expensive tiles, and in a few years you will disassemble the false wall, because the riser is tightly packed and there is no way to clean it.

Preparing for the replacement and eliminating unpleasant embarrassment

In practice, it happens that the replacement of the riser is delayed the next day or even two. The less the unification of the communal building and the older the house, the higher the probability of delays. The reason for this may be, for example, the presence of fastening struts fixing the riser directly inside the floor..

Even if you are completely confident in your own efficiency, you cannot exclude scrupulous situations when one of the neighbors from above will use the sewer. Therefore, carry out work on a weekday and do not be lazy to notify each of the apartments that are located directly above you about your intentions..

Another common reason for tightening is the use of non-standard pipes in the sewer system of a house. It looks like an ordinary 100/110 mm cast iron pipe, even in terms of measurements it corresponds. But then it turns out that the correction for the paint layer was not taken and none of the available adapters is installed tightly.

Dismantling work

The main difficulty in dismantling is to remove a piece of pipe so that later you can depressurize the sockets above and below the replacement section. We recommend that you lock yourself in the bathroom, cover the cracks in the doors with wet rags and provide yourself with good lighting for work. We cover our face with a protective shield – cutting cast iron is not a joke. There will be a lot of dust in the process, so prepare a respirator or a couple of disposable petals.

If you are using a 125 or 180 mm angle grinder, make a horizontal cut on the cast iron pipe at least half the diameter at chest level. Having retreated about 40-50 cm higher or lower – another one. Spread the pipe vertically in two places to get the so-called “window”.

Of course, it is much more convenient and faster to work with a 230 mm grinder, it can often even make a through cut. But in no case try to install larger disks on small angle grinders – they will break with 100% probability. It is better to cut the window “steps”: it will be only a little longer, but much safer. Use the window for cutting out a fragment in the back wall so that the gap is at least 25-30 mm vertically, otherwise the pipe will not turn out normally, but the sealing of the ceiling will definitely fall on your head.

It is in your interests to change the riser together with the neighbors above and below. This way, you don’t have to risk a brand new bathroom finish if they want to replace their lot. This is a matter of exclusively cooperation, but it is better to agree that you undertake the replacement work, and they pay only for the fittings installed directly in their apartment. Thus, for the upper neighbors, you only change the crosspiece, and for the lower ones, the pipe section to the crosspiece..

Accordingly, on the upper floor, we turn off and move the toilet bowl, knock out the cement from the cast-iron sockets with a thin chisel and unpack the crosspiece, simultaneously removing part of the floor seal if the expanded part is embedded in it. If the reinforcement cannot be unpacked, cut it crosswise from the visible side and break it with a sharp steel wedge (cast iron readily bursts from such an impact).

Transition fittings

It’s just great if you have the ability to connect with plastic fittings in the upper and lower zones. But what if you need to connect with cast iron pipes? There are no difficulties for the upper connection if the pipe has a standard diameter: we clean off the paint with a grinder and put on the bell of the lower segment, having previously lubricated with silicone for better sliding.

In this situation, the neighbors from above do not need to bother: the pipe is cut on your side to the maximum depth, after being hit with a sledgehammer, the crack follows the same path and you have the opportunity to dock on your side without removing the segment from the overlap. But, we repeat: in case of replacing the riser on the upper section, the neighbors, most likely, will not be able to dock normally with your pipe, especially if an adapter (taper) of 124/110 mm is installed on it. Therefore, here at least an inspection door is required..

With the lower node, everything is easier: we unpack and remove the crosspiece in our bathroom, trying not to split the socket in which it is installed. Tap the cement paste thoroughly and try turning the cross with a pipe wrench or pry bar. If at the bottom node you have to change to a flat cast iron pipe without a socket, use a plastic shower adapter for cast iron pipes less than 100 mm or a 124/110 mm taper for larger pipes. Sometimes it is possible to insert 110 mm plastic directly into the cast iron riser using only the rubber collars. But you should not unfold the plastic pipe with the socket down and put it on the cast-iron pipe like that – the assembly will certainly leak.

Restoration of a riser in plastic

The most pleasant and cleanest part of the work remains. In the bell of the lower unit, whether it be a cross or a transition from cast iron, we install a 110 mm pipe. It needs to be trimmed in such a way that the edge of the fitting comes out either at the floor level in your bathroom, or slightly lower if you plan to insert a drain siphon into the floor.

1 – cast iron pipe of neighbors from above; 2 – plastic pipe; 3 – clamps for fastening plastic pipes; 4 – a plastic pipe with an elongated socket; 5 – crosspiece; 6 – adapter from a cast-iron pipe to a plastic one; 7 – cast iron pipe of neighbors from below

Proceed in the same way from above: install the cross at the neighbors on top and pack the bends back using plastic compensating adapters with a diameter of 50 mm. Then fit another pipe from below, the end of which will be 120-140 mm above the socket of your cross.

For final joining, an expansion joint is used – a short length of 110 mm pipe with an elongated socket. Before installing it, drill one hole in the wall, placing them on the pipe axis in increments of 50-60 cm. One of the holes should be located just in the center of the expansion joint. Put the expansion sleeve on the pipe, match it with the socket of the crosspiece and lower it, achieving full insertion of the narrowed part.

Now all that remains is to put the brackets on the mountings and fix the riser, after which you can proceed with installing the toilet and performing further wiring. And, of course, do not forget to notify the neighbors about the end of the renovation work..