Water seal for sewerage: classification of water seals and rules for its installation

A siphon is one of the mandatory elements for connecting plumbing equipment to sewer networks. It constantly contains a small volume of water, a water seal - it is simply necessary for sewerage, because...prevents the spread of negative odors. To choose a siphon, it’s worth understanding this issue, right?

We will talk about how the water seal fulfills its duties. The information presented to your attention will help you easily determine the types of device that are optimal for you personally. Reliable information will provide the opportunity to evaluate practical aspects and make an informed purchase.

The article outlines the design differences of the various models with utmost precision and describes the specifics of the installation. Step-by-step instructions, photographs and video guidance will help independent craftsmen in their work.

Operating principle of the water seal

No matter where the hydraulic valve is located in the sewer network, its purpose remains the same:

• block water hammer to reduce the load on sewerage devices and pipes;
• prevent the penetration of unpleasant specific odors into residential premises.

If the water seal (or siphon) is selected correctly, a favorable atmosphere reigns in the house, and the sewer network goes without repair for a long time.

The designs of hydraulic seals of different types differ, but all of them, in one way or another, are pipes with bends of a certain shape, sometimes equipped with additional dead-end or dynamic devices.

One of the most important conditions for the functioning of a water seal is the constant presence of water in its cavity, which acts as a barrier against the penetration of gases and unpleasant odors outside.

The water barrier is constantly in the siphon. If you do not use a device (kitchen sink or toilet) for a long time, the water will evaporate and eventually appear. unpleasant sewer smell in the bathroom or kitchen.

The same thing will happen when you flush for the first time after a long absence. But with constant use, the volume of water in the water seal is constantly updated, which prevents stagnation and, accordingly, the appearance of an unpleasant “aroma”.

The design features of water seals are directly related to their purpose. For example, the following design is typical for toilets: the drain is straight, and the outlet leading to the sewer pipe is inclined

All sewerage devices are interconnected. For example, the right organization fan boner prevents the valve from breaking - a phenomenon when water does not linger in the water seal, but immediately goes into the pipe. In this case, the plumbing fixture loses its protective barrier, and unpleasant odors come outside - directly into the apartment.

Types of hydraulic valves for sewerage

The classification of devices is made taking into account several factors, but the main ones are design features. Based on the technical nuances, we can distinguish six main types of water seals; let’s look at each of them in more detail.

#1: Features of the knee modification

A knee water seal can be identified by its appearance - it resembles the letter U. The advantage of this type is its strength, which allows it to withstand maximum pressure in the pipes. The throughput of the device depends on the cross-section of the pipe, which should not be less than the output of the plumbing equipment.

The main places in the sewer system where it is appropriate to install knee water seals are: bath plums and toilet. Sometimes, instead of one, two siphons are connected.

For the manufacture of knee devices, cast iron and even bronze were previously used, but now it is more expedient and cheaper to use modern material - polypropylene, which is lightweight, reliable and easy to install.

There are different types of knee siphons. Some of them are a single plastic device that cannot be adjusted. If it breaks, it must be dismantled entirely.

Other devices consist of several parts, so if necessary, you can increase the length of the pipes and change their position in order to adjust the volume of water. The position of the pipes is fixed with overhead plastic clamps and nuts.

The knee has two bends - at the entrance and at the exit. The point of the second inflection should be slightly lower than the point of the first (5-6 cm). Sometimes an S-shaped design is used for a more secure lock; its operating principle is the same.

Cleaning knee structures is done in two ways:

• by completely dismantling the device;
• special flexible cable.

Some polypropylene versions are equipped with an inlet for the drain hose of a washing machine or dishwasher.

#2: Benefits of a bottle device

This type of water seal is popular in kitchens for equipping drains under sinks for dishes. During the process of washing dishes and pots, some food waste enters the system, which can cause a blockage.

The design of the bottle model retains food residues, which helps maintain the performance of the sewer system. In addition, the bottle device retains its main purpose - to prevent the appearance of unpleasant odors in the home.

In addition to the pipes that form the basis of any water seal, this type is equipped with an additional element - a “bottle”. This is a kind of container for collecting food waste. The sump is located below the level of the drain pipe, so it is easy to get to it if necessary.

The two parts of the bottle model are connected in the following way: first, the vertical pipe enters the sump located below, then the horizontal pipe exits from the side towards the sewer pipe

The bottle device is made of polypropylene, but is considered weaker in strength than its knee counterpart. The fact is that unreliable connections cannot withstand strong water pressure, so this type is used exclusively in the kitchen and is absolutely not suitable for equipping a toilet or bathroom.

A blockage in the water seal occurs when a dense mass of food debris completely clogs the sump and blocks the path of water. Thanks to the bottle configuration, clearing the blockage is very easy.

It is enough to unscrew the cap nut that attaches to the sump and shake out the accumulated debris from it. Then you need to put the “bottle” in place and tighten the nut more tightly, otherwise water may leak out.

Bottle structures are also useful in terms of preserving items that accidentally fall into the drain. Careless housewives often took their rings out of the settling tanks, slipping off their fingers while washing dishes with soap.

#3: Double-turn water seal device

The design of a double-turn hydraulic seal resembles a knee valve, but has a more complex configuration. The drain pipe is connected to the outlet of the plumbing fixture, and at the junction it is equipped with a filter grid to retain waste, hair and other debris.

Then it smoothly turns into an elbow, which ends with a connection to another pipe. The last element is directed towards the drain and is at a slight angle.

Some double-turn models are equipped with an inspection hole for pipe cleaning, tightly closed with a plug. The function of the hole is sometimes performed by a removable fragment of the knee. The hole is usually located at the lowest point, and the removable part is located at the top

Household double-turn structures were previously made of cast iron, now they are made of polypropylene. Cast iron analogues can only be used in industrial enterprises with increased volumes of wastewater and high pressure in pipes. Chrome-plated parts, which are similar in technical characteristics to polypropylene, look more presentable.

If we compare this model with a bottle alternative, the second option is easier to maintain. However, the double-turn device is more reliable in terms of protection against leakage and, thanks to its simple adjustable design, can be installed even in narrow spaces.

#4: Corrugated model – pros and cons

Among the propylene modifications, there are also corrugated models - durable, flexible, sometimes simply necessary for arranging a sewer system in small spaces. Due to the plasticity of the pipe, corrugated pipes are placed in places where it is difficult to place other types of structures.

It can be rotated at the desired angle and directed in any direction, whereas firmly fixed plastic has only a few position options.

A corrugated water seal is often placed under the bathtub, since less flexible models do not fit in the narrow space between the bottom of the container and the floor. One end is connected to the drain hole, the other to the outlet into the sewer pipe

However, when choosing a corrugated option, you should be aware of its only, but significant, drawback. The ribbed walls of the pipe seem to be designed to collect debris: food debris, hair, pieces of soap, sand and other dirt get stuck in them. Taking this into account, when installing the corrugation, the drain must be equipped with a filter in the form of a fine mesh grid.

If you do not clean the corrugated water seal for a long time, under the influence of dirt and excess weight it loses strength and elasticity. Over time, the folds wear out, begin to crack and let water through.

After installing a flexible siphon, be sure to monitor its condition and clean it in a timely manner. You can guess that the pipe is dirty by the sagging that forms in places where grease and debris accumulate.

#5: How the overflow works

Another type of siphon - with an overflow - can also be placed in a separate category, since it is necessarily equipped with an additional pipe. The main purpose of the overflow equipment is to protect the apartment from flooding if for some reason the water stops going down the drain when the tap is open.

The sinks on which this device is installed have an additional hole - in the upper part of the bowl, under the mixer. When the level of water accumulated in the sink reaches a critical level, liquid begins to flow into this hole and further into the water seal (+)

Bathtubs must be equipped with an overflow system. This method prevents flooding, but, unfortunately, does not contribute to savings. If you want to run a bath and forget to turn off the tap in time, the water, having reached the overflow level, will safely leave the container and go down the drain - along with your money for paying for utilities.

The market offers both economical plastic options and more durable but less elastic metal models. The disadvantages of brass-bronze equipment are the complexity of installation and high cost.

When choosing a device, do not forget to inquire about its throughput. If the overflow cannot cope with the volume of excess liquid, it is useless and even dangerous.

#6: Dry seal design

The design of the so-called “dry” valve is radically different from its hydraulic counterparts.It works on the “nipple” principle and is a threaded pipe with a check valve installed inside. As a result, water entering the device cannot flow back out, just as the smell does not have a chance to leave the pipe.

The installation of such devices is justified on the lower floors of multi-storey buildings, as well as in places where water is used less frequently (in bathhouses).

Dry valves are generally not installed in kitchen sinks, the use of which is highly likely to create blockages. But such devices with water seal work efficiently and last a long time in DIY shower stalls.

The “dry” type valve does not require constant presence of water inside the housing. Even if it functions in conjunction with a knee device, it does not need to be monitored or adjusted

There are several types of dry devices:

• membrane, overlapping after draining the water with an elastic membrane;
• pendulum, tending to close instantly if no liquid is supplied;
• float valves that close the hole when water leaves the drain (acting like the fittings of a flush tank).

The latter are often made independently, arranging sewer lines in bathhouses.

The principle of operation of a float valve is considered the simplest. Light weight keeps the float on the surface of the water. As soon as it drains, the float moves down and blocks the drain.

If the sewer lines suddenly dry out due to infrequent use, thanks to the dry seal, the unpleasant smell will not bother you.

Guidelines for choosing a water seal

If you are installing or replacing plumbing fixtures (bathtub, sink or toilet), you will definitely need a siphon.

To select a device that fully complies with plumbing, it is necessary to take into account a number of factors, including:

• dimensions of the assembled device;
• siphon type;
• the material from which the pipes and fasteners are made;
• number of drains or additional connections;
• protection against blockages;
• diameter of inlet and outlet;
• presence or absence of overflow.

Suppose the most suitable option for a kitchen sink is a bottle model that traps food particles. You can also use a knee device, but then all the waste will flow into the sewer pipe, and over time there is a risk of blockage.

For both sinks and bathtubs, models with an overflow are considered more effective, preventing room flooding. The recommended material is polypropylene, but for finishing the external parts it is better to buy models with chrome parts

If the project involves installing a sink or washbasin with two sinks, a device with two drain points will be useful. Its operating principle is the same, the only difference is in the design.

Before purchasing, be sure to measure the size of the space where the installation will take place. It happens that the siphon simply does not fit in the allotted space (this is especially true for the close gap between the bathroom and the floor). If you choose the right water seal, there will be much fewer problems with its installation and repair.

If the water seal from the siphon is pulled into the sewer, the system is modernized by installing vacuum valve:

Installation instructions for automatic siphon

Installing a hydraulic bottle seal under a kitchen sink is quite simple, but under a bathtub is a little more difficult due to the inconvenient location of the drain system. We present instructions for installing an automatic siphon for the bathroom - an advanced device that you can install yourself.

A complete set can be purchased at your local plumbing supply store. It consists of three significant parts: 1 – plastic design water seal + corrugated pipe; 2 – details for decorating the overflow; 3 – fastening elements for draining

First, we will equip the overflow hole. To do this, take the elastic gasket that comes with the kit and insert it into the hole on the wall of the bathtub. For a tighter connection, you can use silicone sealant.

We fix the overflow structure in the hole by screwing the chrome element on the outside. It is equipped with a rod on which the lamb will be held

Then we take the next part - the lamb - and try to carefully secure it to the rod with a bolt.This will require a small flathead screwdriver that can fit through the small hole in the side of the wing.

We put the wing on the rod, insert the end of the screwdriver into the side hole and with a little force, but very carefully, tighten the fixing bolt

Next, we move to the lower part and take fittings to design the drain hole.

We pass the plastic part under the bathtub and insert the end with the rubber gasket into the hole. Place a standard chrome-plated part with a mesh on top of the resulting hole.

Among the fasteners we find a long mounting screw, which is responsible for fixing the siphon, and screw it in from the top side, holding the structure from below.

First, tighten the screw by hand, then tighten it with a wrench, but very carefully so as not to strip the thread. After completion, we check the strength of the installation

All that remains is to screw on the water seal element. First, we string a rubber gasket onto the plastic outlet of the drain, then insert the knee valve. Tighten the outer plastic nut - the structure is ready.

Appearance of the installed automatic siphon. Two pipes extend from the drain hole: one (corrugated) - to the overflow hole, the second (curved) - the actual knee water seal

Lastly, we attach a polypropylene pipe (straight or corrugated) to the water seal, leading to the sewer pipe.

We test the system - pour a full bath of water and check the operation of the overflow and drain hole. Let's see if there are any leaks. If we find a leak, we tighten the nuts more tightly and coat the joints with sealant, but on the condition that they do not have to be opened in the future to clear the blockage.

Detailed sequence of work and rules installing a siphon under the bath will familiarize you with the article, the contents of which we recommend that you familiarize yourself with.

Conclusions and useful video on the topic

To ensure that the installation process goes smoothly and without the errors that plague amateur home plumbers, we suggest watching useful videos.

Video #1. The best option for equipping a kitchen sink:

Video #2. Installation of a siphon when installing a bath:

Installing a sewer siphon is a process that even a novice in plumbing can handle. If you correctly decide on the type of water seal and carefully study the instructions, all that remains is to screw on a few parts. Work for half an hour - and a comfortable environment in the house and the absence of an unpleasant odor - for years.

Please write comments in the block below. We and site visitors are interested in your stories, advice, and short photo reports about installing siphons with your own hands. Ask questions about controversial issues that you may find in the article.