Replacing pipes in a toilet from A to Z: design, selection of building materials, installation work + error analysis

Replacing leaky toilet pipes yourself is not easy, but it is possible.The main problems here arise from the cramped space in the bathroom. Many owners do not want to get rid of the old toilet, but replacing pipes in a toilet with already installed plumbing is still a pleasure.

We will tell you all about the rules and specifics of replacing communications in the bathroom. We'll tell you what materials an independent home craftsman will need to stock up on. The article we presented describes in detail the replacement technology and provides useful recommendations, adherence to which will ensure the quality of the assembly.

Pipe condition diagnostics

Before you go to the store to buy new pipes, you need to think again about whether such repairs need to be done at all and in what volumes they should be carried out. If you plan to work in a toilet located in a private house, then this is one situation. Nothing will interfere with the owner-master here.

But when working in a high-rise apartment, there will be many problems. When replacing water supply risers in the apartment You must coordinate your actions with your neighbors in advance. And this is not only a tribute. There are several points here that, if you forget about them, you will soon run into serious problems.

Changing the risers in an apartment toilet should only be trusted to the plumbers of the company servicing the apartment building; they are better informed than outsiders about the condition of the pipes in this particular building

First, the water supply pipes can be shut off in the basement of the entrance for several hours without asking anyone.During the day, plumbers do this quite often in apartment buildings. Neighbors are at work during the day, most of them don’t even know about the interruption in water supply. However, you should not dismantle the sewer riser without warning.

Even if the cold water in the house is turned off, it still remains in the toilet tanks. And if the sewer riser is dismantled, all the fecal matter that will be washed away on the floors above will certainly end up in your toilet.

It is better to communicate with your neighbors in advance and warn them about the work being carried out so that they do not use the plumbing for a couple of hours. The second point is the pipes on the site in the interfloor ceiling. These riser spots are considered the most vulnerable and most problematic. This is where metal rusts the fastest.

When completely replacing pipelines, they must be routed from above and below through reinforced concrete. That is, welding and other connections of new pipes with old ones may have to be done in neighboring apartments on the floor above and below.

Having learned about the repairs being carried out, the neighbors may well decide to also change the risers at the same time as you. This will allow you to save a little on materials and calling plumbers who will come to turn off the water in the basement during repairs.

If sewer and water pipes are replaced in several apartments at once, then for each owner it will be cheaper than calling plumbers alone

The third point is the condition of the pipes. Often water supply and sewer risers look useless only from the outside. But when cutting an old iron pipeline, there are often cases when it is covered with rust only on the outside.

If it does not leak, then it is often not worth replacing it.Everything inside can be perfect; the walls are still capable of lasting a couple of decades.

This happens when there is bad ventilation in the bathroom and toilet. Condensation accumulates on the outside of metal water pipes, leading to rust. However, corrosion only affects the outer surface of the pipeline. Then you just need to clean it with sandpaper and paint it with good paint.

Changing pipes in such a situation is just wasting money. A cast iron sewer riser should be replaced with a plastic one if it is externally damaged. Old cast iron is more durable and less noisy than modern plastic.

Options for laying pipes in the bathroom

If the toilet in an apartment or cottage is not combined with a bathroom, then special problems with preparing the pipeline layout are unlikely to arise. As a rule, there is only one toilet and there are two risers, from which it is necessary to connect a couple of pipes to this single plumbing fixture.

However, next to the wall there is usually a kitchen and a bathroom, where pipelines also need to be laid. It is with their wiring that there are mainly difficulties when replacing pipes.

Plumbing fixtures are connected to water sockets using a rigid or flexible method (via drain hoses); toilets are connected to the sewer system only using the first option or using corrugated pipes

There are two technologies for laying pipes in the bathroom:

1. Outdoor.
2. Hidden.

The first method is easier to implement, and the second is better from an aesthetic point of view. When laying pipelines hidden, you will have to trench the walls, which means dirt and additional preparation time.

The best option is to lay the pipes in the toilet according to the external scheme, and then cover them with a decorative box.Moreover, the risers will still have to be covered with decor. If you leave them open, the interior of the bathroom will look ugly.

With a hidden gasket, any leak immediately turns into a headache. We have to start all over again. You will have to remove the cladding, break down the walls and replace the pipes again.

A good option for outdoor installation with decorative false walls and boxes. The latter have inspection hatches and are easily removed if necessary, if you need to get to leaking pipelines.

The sewer pipe is laid with a slope towards the riser to ensure gravity flow. According to the rules piping in bathrooms in places where plumbing fixtures are installed, tees are inserted into it with the sockets positioned towards the movement of the drains.

According to building regulations sewer pipe slope selected based on the diameter of the pipeline. The smaller the cross-section, the more the latter should be inclined.

For an indoor sewer pipe with a diameter of up to 50 mm, the slope is 3 degrees (3 cm in height for each linear meter). For products with a cross section of 50–110 mm, it is recommended at 2 degrees, and for analogues with a cross section of 110–160 mm – at 0.8 degrees.

Plumbing is connected to the water supply:

• according to a sequential scheme;
• through the manifold at the riser.

The manifold version is more expensive, but the pressure at each water outlet with such a layout is always the same. In this case, the water pressure in the taps and shower does not fluctuate when you turn on the washing machine or fill the toilet tank.

When using a collector circuit for supplying water from the riser to the plumbing fixtures, a lot of pipes will have to be installed, and all this equipment is usually located in the toilet

Water outlets are attached directly to the walls or to cross beams (metal plates with holes for fasteners). In this case, the outlet for the toilet in the toilet is most easily done with a hose.

On the cold water supply pipeline passing by, a tee is simply inserted with a terminal having an external or internal thread. Ideally, pipes should be installed parallel everywhere, without intersecting each other.

A shut-off valve is installed immediately from the riser and at the end of each water supply outlet. This is necessary so that, if necessary, you can turn off only one plumbing fixture to replace or repair it.

From the water supply riser, first place ball valve, then a coarse filter, and only then a counter. The simplest and cheapest filter is a mechanical one without backwashing (with a small straight or oblique “branch”, with a dirt mesh inside).

From time to time you will have to unscrew the lid on it with a wrench to wash out the stainless steel mesh that accumulates sand and rust. The self-washing filter is large in size. It must be connected to the sewer, and a bypass bypass must be installed parallel to it.

If there is not enough space on the toilet wall, then it is better to refuse this option. All this together is called the “input node”. After it comes a pipe for connecting plumbing or a manifold.

Procurement of building materials

There is no ideal building material. In each case, a different option is selected that is most suitable for specific conditions.

When replacing pipelines in a toilet, you must purchase the pipes themselves, fittings and taps for them in advance. It doesn’t hurt to design in advance camouflage box and purchase finishing materials for it.Then all work will take a maximum of one day.

Selection of pipes for sewerage

It's easiest with sewer pipes. If the existing cast iron riser does not have cracks or holes, then it is not worth replacing. Otherwise, you should choose plastic tees and bends.

These pipe products are light in weight and easy to install. They are connected to each other in a socket with a rubber cuff. The most difficult thing is to cut such pipes with a hacksaw into a piece of the required length, not forgetting to treat the end from burrs.

Cast iron sewer parts should be separated carefully; this metal is very fragile - hitting it with a hammer or pressing a break with a large lever is prohibited

Polymeric ones are sold for installation in the toilet. sewer pipes from:

1. PVC.
2. Polypropylene.
3. Polyethylene.

The cheapest option is polyvinyl chloride. But polyethylene and polypropylene are more resistant to household chemicals and temperature changes that occur when hot water is drained down the drain. However, in general, any of these materials is suitable for a toilet in an apartment or private house.

Previously, cast iron pipes were connected with cement or sulfur. In the first case, the joint will have to be slowly peeled apart with a screwdriver, and in the second, it will have to be heated with a torch.

One element should be removed from the other carefully by loosening it back and forth, otherwise the socket will crack and you will have to change a lot more pipes. To connect plastic and cast iron, an appropriately sized rubber cuff will be sufficient.

Types of pipes for hot water supply and cold water systems

Water pipes for replacement in the toilet can be taken:

• stainless steel;
• copper;
• polypropylene;
• polyethylene;
• polyvinyl chloride;
• metal-plastic.

Steel and copper pipes will have to be connected by welding (soldering), so they are rarely taken for self-installation. Stainless steel is often used by plumbers to replace old iron water pipe risers.

This option is the most reliable. When properly welded, the joints between new and old sections of such a pipe almost never leak.

When independently replacing toilet pipelines for hot water supply and hot water supply, it is recommended to choose plastic pipes; they are cheap and easy to connect in various ways

For cold water supply in an apartment, plastic pipes should be purchased with the PN10 marking. This thin-walled version is designed for a working pressure of 1 MPa and water temperatures up to +20⁰S. For cold water supply this is quite enough. For DHW you will need an analogue with PN20 and higher. It has thicker walls and higher operating parameters in terms of temperature and pressure.

PP pipes are joined by diffusion welding using fittings and butt joints. The connection is permanent. For installation of metal-plastic, compression or press fittings are used. This is the simplest material for self-assembly of a pipeline. Plus, if necessary, the water pipeline can be easily disassembled for replacement or insertion of new plumbing.

PVC is mounted on glue with a butt or fitting connection. PE (HDPE) is connected at home using electrofusion welding or compression couplings.

Metal-plastic pipes are good because they can be bent in the corners of the room; they are the most flexible of all plastic analogues. However, fittings for them will be expensive. Polypropylene water pipes are cheaper to connect, but due to the large thermal expansion, they often sag during hot water supply. PVC is cheap, but to supply hot water you will have to choose a different option.

How not to make mistakes when dismantling/installing pipes

When planning to replace pipes in a toilet, you should remember that the matter will not be limited to one room with a toilet. The sewer pipeline will definitely have to be completely changed.

Separately changing sections of the water supply only in the toilet, without affecting areas in the bathroom and kitchen, is also hardly a reasonable idea. If you update the pipes, then immediately completely from the riser to all plumbing fixtures without exception.

In most cases, the sewer pipe in the toilet is only a small section of the entire intra-apartment drainage system

Disconnect cast iron tees and insert new plastic bends into them using exclusively rotational movements. Cast iron is too fragile to put much pressure on it, much less hit it with a heavy tool. But if such a riser is planned to be completely removed, then breaking it into separate pieces will not be difficult.

All existing flexible braided eyeliners, going to the faucet or toilet should be thrown away immediately upon dismantling. Their service life usually does not exceed five years.

It’s better to replace them with new ones without hesitation. The situation is similar with all old shut-off valves. If it has served for more than 3-4 years, then replacement is required. It's not worth the risk.

The joints of sewer outlets and pipes, as well as the points where plumbing is connected to it, must be sealed with cuffs or silicone, otherwise sewer stench will fill both the toilet itself and adjacent rooms

Shaped parts must not be cut or altered in any way. Their bell should face the movement of wastewater.

Without exception, all water supply pipes must end with shut-off valves. Ideally, each plumbing fixture needs its own ball lock fitting.This will greatly simplify life in the future when connecting and replacing equipment in the bathroom and kitchen.

Before cover the pipes with a box, the system should be pressure tested. It is necessary to supply water through all pipelines and turn on all plumbing fixtures. And then you need to check the joints for drips and leaks. Only if they are completely absent can you begin finishing the toilet.

Conclusions and useful video on the topic

To make it easier for you to understand all the nuances of replacing pipes, we have made a selection of videos that explain all the subtleties and tricks of the process.

Video #1. How not to change pipes and plumbing:

Video #2. All about the correct installation of internal sewerage:

Video #3. Tricks for replacing metal pipes with plastic ones in a combined bathroom:

Replacing old sewer and water pipes in a toilet is easy. There are some subtleties in this work, but if you wish, you can do everything yourself.

Just before dismantling the existing risers, you should take a closer look at them. Old pipelines can often last for many years. This is especially true for the sewer system.

Would you like to talk about how you changed communications in your own bathroom? Do you have valuable information that may be useful to site visitors who want to change the pipes themselves? Please write comments in the block below, publish your photographs, and ask questions about controversial issues.