Ventilation check valve: purpose, types, installation

Residents of apartments in multi-storey buildings often face the fact that odors from neighbors through ventilation ducts get into their rooms. An unpleasant situation, which will help to cope with a check valve for ventilation. How it looks like, how it is arranged and where to put it, and we will discuss.

Why do you need a check valve on the ventilation?

With normal operation of exhaust ventilation, the air moves from the room to the street. Exhaust openings are located “in dirty or wet” rooms – bathroom, kitchen. The task of this part of the ventilation system – to remove odors and excessive humidity to the street. But sometimes there is a situation when through the exhaust ventilation air goes in the opposite direction – enters the premises. This moment is called overturning of the draught and with this phenomenon try to fight.

Why is it necessary to fight with the reverse draught? In the case of apartments, it is fraught with the arrival of odors from neighbors, which is very unpleasant. If we consider private houses, in them portions of outdoor air in winter reduce the temperature. The second point is more dangerous and unpleasant – when the reverse draught can extinguish the boiler, from the chimney can return to the room products of combustion (and carbon monoxide too). In any case, the reverse movement of air flow is incorrect operation of the ventilation system and this phenomenon must be combated. Check valve on the ventilation is just put to block the movement of air in the wrong direction.

Device and principle of operation

Check valve for ventilation is most often a section of round or square cross-section pipe. In this section is movable – usually on the axis – installed a piece of material (metal, plastic, mica) of suitable shape. This is the valve itself. In the closed state it completely covers the pipe cross-section, in the open state it should create as little resistance as possible. To make everything work properly, it is necessary to put it so that when there is a reverse flow of air, the valve closes.

Not only valves in the pipe are put on the ventilation – there are options for the ventilation grille and the fan. In the case of a vent grille, a thin plastic or mica membrane can be used, which is attached to the grille. There is also a butterfly valve and louver-type slats. The same type of backflow preventer can be used on the exhaust fan.

The principle of operation of this device is simple: with normal air movement, the valve is open and creates a small resistance to the air flow. When a back draft occurs, it closes, preventing foreign odors or cold air from the street from entering the room.

Trouble that can arise

It seems clear and logical: extraneous odors in the apartment – this is very unpleasant. The overturning of the draught in a private house is not less unpleasant, but also dangerous. In principle, with a properly designed system, such phenomena should not occur and the causes of occurrence should be fought. But not everyone has the opportunity and resources. It is easier to put a check valve for ventilation. This is true, but there are nuances that are worth knowing.

• Installed in the ventilation hole, the valve interferes with natural ventilation. If you want the natural exhaust to work, you need to think about the connection so that the valves do not interfere.
• Even “quiet” valves made of plastic, when they are closed, they slam, sometimes making quite loud noises. These pops are the stronger the stronger the draft. In variable winds, they are very annoying. So something will have to be worked out to make the valve “quieter”.

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• Some fans or kitchen hoods have a built-in check valve. If the standard one does not suit you for some reason, it should be removed. Then a separate one can be installed. Two valves on the same channel may not “get along”. More precisely, the exhaust duct is unlikely to work.
• For normal operation, the check valve should be regularly serviced – cleaned, checked, axles lubricated. Given that it is not always easy to get to it – it is at least inconvenient. So make sure you have access for cleaning and inspection.

As you can see, put a check valve on the ventilation – does not mean to solve the problem once and for all. You will have to monitor the condition of the system and put up with the disadvantages of this solution.

Types

The check valve on the ventilation can be made of metal or plastic. Metal is most often galvanized, less often – stainless steel. There is still a small group with a plastic body and a metal flap – called most often “combined check valve for ventilation”.

How to choose on this basis? Simple. You choose the material from which you have made a duct. There may be models of round or square cross-section. Here again, choose the same shape as the existing/planned air ducts. Thankfully, the dimensions are the same as the standard pipes used for ducts.

Opening method

Check valves can be opened in different ways:

• Manual. The dampers are opened or closed manually, for this they have a special lever. This is not too convenient, in addition, due to design features, they are not hermetic, so that they can not completely block the penetration of foreign odors.
• Electrically driven. Forced to open simultaneously with the inclusion of a fan or hood. Suitable only for ventilation systems with forced air removal (without natural circulation).
• Mechanical. The most common type. Open and close from air movements. They are put both in a pair with a fan or exhaust, and on natural ventilation.

Manual check valve can be put on the exhaust pipe with forced air discharge, going out to the street. This is sometimes done in this way – not in the ventilation duct, but outside through the wall. In this case it is better to have a damper, which will be opened only when the hood is working. It is possible, of course, to put a normally closed damper, but in cold weather it will freeze and cease to fulfill its functions. Therefore, manual opening is more reliable in this case.

The most common are mechanical check valves. They are installed in about 90% of cases. Structurally, they can be of different types. Here we will talk about them in more detail.

Forms of mechanical valves

Different flaps can be installed in the check valve. The shape of the flap largely determines the force at which it will be pushed back. If the damper will be operated with a fan or exhaust, it is important that the weakest mode of operation of the fan can open the damper. It is said that the fan should push the damper through. If you want to maintain natural ventilation, it is essential that the damper can be “triggered” by even the weakest air movement.

The designs and shapes of mechanical vent check dampers can be:

To choose a valve for ventilation, indeed, is not easy. If you are guided by what most people use – you have to stop at the clapper. For all its disadvantages, it works more reliably, opens even with natural ventilation. The most effective way to make the clapper quieter – take silicone sealant, apply it to the thrust ring on the body (do not apply it to the disk, as it will become heavier, so it will be more difficult to turn). Lubricate the valve disk with soap solution and press it against the sealant ring – until it starts to polymerize. Then the valve is pushed back, we get a sealing ring, which dampens the pops. The result – almost silent closing, and almost airtight.

Valve on the ventilation: where and how to put it

If the ventilation system is made without the use of fans and hoods with motors, it is called natural. To make everything work, valves are installed immediately at the outlet of the channels to block the back draft. To maintain normal circulation, it is desirable not to use grilles that block the valve. Yes, this option looks better, but ventilation suffers. Most likely, to work with a small draught, it will simply not work.

If you still want to install a decorative ventilation grille in front of the valve, you will have to put up with the deterioration of ventilation, slower removal of odor and excessive moisture. Only installing a grille/valve with a larger diameter than calculated can help. In this case, air exchange will not be affected.

In the case of forced ventilation, the check valve can be either upstream or downstream of the fan. This choice depends on the type of system and fan. Since duct fan models are rarely used in private systems, it usually turns out that the damper stands after the fan in the pipe. How far away is not important. The main criterion for choosing the installation location is ease of maintenance, since the damper will have to be periodically cleaned and checked.

Installation in a kitchen with a hood

When installing a forced hood in the kitchen, many people want to keep and natural ventilation. To do this, it will be necessary to install a tee at the entrance to the ventilation channel. To one of its inputs connect the hood with a check valve, in the second put only a check valve. As you can see, the system is not too complicated, but it works.

Why should there be a check valve on the hood too? Because if there isn’t one, backflow of air can pass through the hood. Yes, it will not happen every time, but in case of a strong flow, it will happen.

When arranging this unit, try to make sure that the check valve for ventilation is located as high as possible under the ceiling. As a result, the warmest and most humid part of the air will be diverted, which is very important for the kitchen.

For bathroom and toilet

Ventilation of the bathroom can have its own exhaust duct – then everything is easy, simple and clear. Before entering the ventcanal, we put a check valve to block the flow of air that will move into the room. But not all apartments can boast individual shafts for the bathroom and toilet. In some houses of old planning, the exhaust duct is only in the toilet. Ventilation of the bathroom is made by conducting a box through the wall. In this case, the check valve for ventilation is put not only at the exit to the vent channel, but also in the channel between the bathroom and the toilet. This will prevent the entry of unpleasant odors into the bathroom.

There is an even sadder situation: when the exhaust channel is generally one and it is located in the kitchen. Actually, the logic of the installation does not change – it is necessary to put devices so that odors from one room do not get into the other.

One check valve for ventilation put on the outlet to the dome hood (or on the channel that takes the air out of the kitchen), the second – on the pipe that comes from the bathroom. As you can see, if you understand the logic of operation, you can determine the most successful place of installation yourself.