What is a non-return valve in the hood

Installing a non-return valve in the ventilation: the algorithm of actions

This work is not complicated and even a novice home handyman can cope with it. For installation you will need self-tapping screws, an electric screwdriver, construction silicone in a tube and, actually, the valve itself.

How to install a check valve on the ventilation:

The principle of operation of the ventilation grille with a valve

The grille with a check valve consists of three main parts: a fixed part, a movable part and a flange, to which the duct is connected.

Fixed part is a grid that plays a decorative and protective role, partially hiding the valve and protecting it from mechanical damage. Is made of plastic, is usually rectangular in shape and covers a part of the wall in addition to the ventilation shaft.

The moving part looks like a rectangular or circular petal, opening in one direction. Sometimes there is a “butterfly” shape. As the system is operated in conditions of high humidity, the check valve is made of plastic that is not afraid of aggressive influence of moisture. Metal structures are of artisanal origin and are not particularly reliable.

The flange is a circle with diameter of 110-150 mm and is intended for connection of the valve to the air duct.

Trouble that may arise

It seems clear and logical: strange smells in the apartment are very unpleasant. Tipping 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 should be addressed. But not everyone has the capabilities and resources. It’s easier to put a check valve for ventilation. It is, but there are nuances to be aware of.

  • The valve installed in the vent interferes with natural ventilation. If you want to work natural ventilation, you have to think of the connection so that the valves do not interfere.
  • Even “quiet” valves made of plastic, when closed, they slam, making sometimes quite loud noises. Those popping noises get louder the harder the draft is. In variable winds, they are very annoying. So we’ll have to think of something to make the valve “quieter”.
  • This is the quietest valve. an elastic membrane. but not very reliable

As you can see, putting a non-return valve on the vent. does not solve the problem once and for all. You have to monitor the condition of the system and put up with the disadvantages of this solution.

Check valve on the vent can be made of metal or plastic. Metal. this is most often galvanized, less often. stainless steel. There is also a small group with a plastic body and a metal damper. called most often “combined check valve for ventilation”.

Check valve for ventilation is made of plastic and metal

How to choose according to this feature? Simply. You choose the material of which you have made a duct. Can be circular or square. Here again, choose the same shape as the existing / planned ducts. Goodness, the dimensions correspond to the standard pipes used for ducting.

How you open it

Check valves can open in different ways:

  • Manual. Dampers open or close manually, they have a special lever for this. It is not too convenient, in addition, because of the design features they are not tight, so they can not completely block the penetration of odors.
  • Electrically operated. Forced to open simultaneously with the fan or hood. Only suitable for forced exhaust ventilation systems (without natural circulation).
  • Mechanical. The most common type. Open and close from the movement of air. Can be paired with a fan or extractor fan, as well as for natural ventilation.

In addition to the mechanical, there are manual and electromechanical opening

A manual non-return valve can be installed on the exhaust pipe with a forced air vent to the street. Sometimes they do it this way. they do not go to the ventilating duct but to the street through the wall. In this case, it is better to have a damper that will be open only when the hood is in operation. You can, of course, install a normally closed valve, but in the cold season it will freeze and stop working. That is why the manual opening is more reliable in this case.

If the exhaust is led outdoors through the wall

The most common. mechanical check valves. They are installed in about 90% of cases. Structurally, they can be of different kinds. Let’s talk about them in more detail.

Mechanical valve shapes

Different dampers can be installed in a check valve. The shape of the damper largely determines the force at which it will push back. If the valve will work with a fan or hood, it is important that the weakest mode of the fan can open the damper. It is said that the fan must push the valve through. If you want to preserve natural ventilation, the flap must be able to “trigger” even a slight movement of air.

The designs and shapes of mechanical non-return valves for ventilation ducts can be as follows:

    With a solid pivoting flap on an axis (flap). This is the most common variant. This is a disc or rectangular piece that is movably mounted on an axis. Sometimes the axis is in the center, sometimes it is offset. This is a fairly popular model, as it has no springs and can be installed in a system with natural air circulation. But there is a problem: when you close the flap you hear a popping noise. The stronger the draft, the louder the pop. It’s annoying even during the day, and at night it even disturbs your sleep. Because of this feature this model is often called the “clapper”. And the rubber and foam gaskets do not help much. When installing on natural ventilation, the axis is oriented vertically. It is important because in such position the force for opening is minimal.

Choosing a ventilation valve is really not easy. If you go by what most people use, you have to stop at the flap. With all its disadvantages, it works more reliably, it opens even with natural ventilation. The most effective way to make a firecracker quieter is to take a silicone sealant, apply it to the stop ring on the body (do not apply it to the disk, as it will become heavier, so it will be harder to turn). Lubricate the valve disk with a soapy solution and press it against the sealant ring. until it begins to cure. Then the valve is moved away, we get the O-ring, which dampens the popping. The result is a nearly silent closing with a hermetic seal.

Variety of valves

These are not the only differences, there are also models:

  • With manual control, the device is installed in large enterprises, where there is high air movement. Automatic products actuate without user intervention, this option is more suitable for installation at home.
  • They differ in the way they are installed. There are horizontal and vertical variants.
  • Round and rectangular products are available. To choose the right option, it is important to understand that the shape depends entirely on the features of the air channel section size.
  • Also the flow capacity is taken into account. Here everything depends on the volume of air that passes through the valve.
  • The last difference. the material of manufacture. Plastic ones are suitable for installation in houses and apartments, as they make less noise when working. For office buildings and industrial enterprises it is recommended to install metal products. They are larger in size and have a high discharge capacity.

Reasons for back drafts

Sometimes it is impossible to ventilate the room because of returning air from the ventilation duct with all sorts of smells. This happens if the balance of incoming and outgoing air is disturbed due to a clogged or narrowed common ventilation duct. And also because of the installation of fans with high power in other apartments, exhaust air does not have time to be exhausted outside and comes back from other rooms. The upper floors are often affected. Since the kitchen and bathroom ducts are connected, the bathroom fan installed in your apartment causes a backdraft toward the kitchen.

In the houses of the old buildings were designed shafts, designed for a smaller air flow capacity and can not cope with the large volumes of modern powerful hoods. It helps to organize an acceptable air exchange in the room with the help of non-return valve for ventilation. It helps to change the amount of air withdrawn and allows it only in one direction, blocking the flow back. Thanks to him all sorts of smells from adjoining apartments do not fall into the house, and from the street do not fly dust, fluff and insects.

Check valve for ventilation with their own hands

Do I have to buy a ready-made non-return valve? It’s up to you to decide this question. As you guessed, to make such a non-return valve is quite feasible for almost any man.

complex designs make their own makes no sense for the reason that it will take a lot of time and costs will be disproportionately higher than when buying a ready-made product. The price difference on the valves is quite noticeable. The simplest designs are ten times cheaper than more complex counterparts.

The point is big: the design of the valve is calculated under a particular model of the fan, so it will work perfectly in tandem with this fan. In another set mismatch can be very bad for one of the devices.

Particularly relevant installation of check valve ventilation with their own hands for the occupants of the upper floors of houses, where the problem of tightening the “strange” smells through the air ducts of general exchange system is widespread.

For the base of the kitchen ventilation check valve is suitable thick plastic or textolite. You will need a plate of a size that overlaps the outlet of the exhaust duct and a thickness of no more than 4 mm. On the plate is made marking: a grid the size of the hole ventilator, as well as holes for attaching to the wall (in the corners) and to secure the fan.

The larger the mesh lattice, the tighter the material for the blades must be!

To ensure that the air between the base and the fan does not “walk”, rubber gasket is used.

To prevent not only the back draft in the ventilation of an apartment building, but also the penetration of insects, a fine plastic mesh or even kapron from pantyhose is attached to the base grill. The latter can easily be replaced. And so that the tenants are not bothered by vibration from the fan engine, the installation uses shock absorbers made of rubber.

The leaves are used from thick polyethylene (not less than 0.1 mm). The film should be perfectly smooth, the smallest ripples will break the airtightness of the ventilation, and the back draft in the apartment building will resume. The flaps can be fixed on the adhesive tape with a fabric base.

To between the home-made plastic check valve for ventilation and the wall was not a gap, use self-adhesive foam tape. During operation, you must periodically clean or replace the plastic mesh, clogged with dust.

If properly made, such a homemade plastic check valve for ventilation will last more than a year. And the tenants will get rid of reverse thrust, typical for the ventilation of apartment buildings for a long time.

The use of check valves for different ventilation systems

Regardless of the type of ventilation, whether it is a natural supply and exhaust or a mechanical system. in it can occur back draft.

For natural ventilation, where ventilation ducts are used, check valves are used, which are particularly sensitive to changes in the direction of air masses. For quality air exchange it is better to make installation of a non-return valve for ventilation at the same time with the installation of ventilation ducts.

Example of arrangement of exhaust ventilation using non-return dampers

non-return, valve, hood

Installation of non-return valve for ventilation in an apartment with natural air circulation is made in the walls between the rooms. Openings in the apartment walls are usually made near the doors and grilles for non-return dampers are inserted to control the airflow.

Fresh air intake ventilation, which consists of a duct mounted in the outer wall, equipped with a grille for air intake from the street side. The filter cleans outside air and a non-return valve device controls supply air volume and helps to maintain room temperature. At the same time the installation of non-return valve allows you to do not have to resort to additional ventilation of the premises where plastic windows are installed, the air exchange will be sufficient.

Mechanical exhaust ventilation in the kitchen with exhaust air to the outside

You can choose the fan, not only calculating all the characteristics yourself, but also focusing on a selection of the most interesting and practical models.


This device of Russian manufacture has excellent performance and noise figures.

The ABS-plastic housing is UV-resistant and sealed thanks to the rubber seals around the perimeter, and the internal components are protected from moisture and dust. ERA FAVORITE 4C-01 has a double-leaf valve, which will not let the air in the opposite direction, against the fan. That way the smells from the ventilation shaft do not penetrate into the room. The motor is protected from overheating by fuses. In terms of its parameters, the device fits perfectly into small rooms. Mounted overhead.

non-return, valve, hood

Soler Palau SILENT-100 CZ DESIGN

Stylish, well thought-out to detail fan from a leading Spanish brand. Its housing is absolutely leak-tight, the outer casing is flat, making the unit easy to care for. The device can operate without any problems in rooms with temperatures up to 40 °C. Motor is mounted in the housing with rubber-metal bushings. They absorb some of the vibration load, making the fan almost noiseless. The valve prevents the return of air from the outside 100%.

Judging by the reviews of users and service experts, we can draw a conclusion: the motor is reliable and will never break down over the entire operating time of the device.


Thanks to the additional rubber pads, the AURA DiCiTi 4C MR runs very quietly. They make the unit’s casing airtight. The motor is reliable, needs no extra maintenance and has optimum performance for domestic sanitary installations.

This fan has a Fusion Logic “smart” timer that can be programmed according to the needs of the individual user. This is a nice feature that allows you to organize the operation of the device to squeeze the maximum efficiency out of it with minimum power consumption.

What it is and what it is for?

A non-return valve is a device to be installed at the outlet of the air duct, consisting of a casing and a butterfly valve. The casing, in its turn, is fitted with a decorative grating that covers the internal parts and fixing elements of the construction. The flap has the ability to open under the pressure of the outgoing air and return to its original position when there is no flow.

Check valves come in standard sizes and are compatible with all types of ductwork. The material of these appliances is mostly plastic. There are also metal models, but the scope of their application is often limited by the humidity level of a particular room. Although galvanized and chrome-plated products have an anti-corrosion coating and, along with plastic products, can be used in bathrooms, showers and kitchens.

non-return, valve, hood

what is a non return valve

The principle of operation of check valve is the following: contaminated air goes out of the room and getting through the overlay in the body of the device, presses on the damper and opens it. As soon as the pressure of the outflow drops, the flap closes and provides a solid barrier to dust, odor and small insects. In addition, the use of even the simplest leaf valve noticeably reduces the level of outside noise coming from the adjacent room or from the street. The unit can be attached to the internal or external end of the duct, or behind the fan if installed in forced air circulation systems.

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