When arranging an autonomous water supply system, it is necessary to carefully select not only the pump, but also a variety of protective pipe fittings. Among the important devices, one of the significant places is occupied by the check valve for the pumping station, which helps to maintain a stable pressure in the hydraulic system.
It prevents premature wear of pumping equipment and prevents malfunctions.
Types and purpose of back-stop valves
The dimensions of the check valve are small, but without this trifle the pressure in the water supply system will be impossible to maintain. It belongs to the category of pipe fittings, whose main task is to prevent the reversal of the flow of water in the pipes of the water supply system.
Household pumping equipment is not designed for its movement in an abnormal direction.
The non-return valve is used to allow water flow in only one direction, completely blocking its backward path (+)
There are models of pumping stations on the market, in which the manufacturers complete the check valve. These options include a suction hose with a non-return valve. But in most cases, this armature has to be purchased independently.
Similar gates are placed both on the suction line and on the inlet to the domestic water supply system immediately after the pump with a hydraulic accumulator or in front of the pump station.
Depending on the installation location in the scheme of the water supply system, non-return valves are divided into:
- Bottom line. Prevent the reverse movement of the water raised from the source when turning off the pumping equipment. They create conditions for the operation of the unit without constant filling with water before starting it and the suction line.
- Piping. Among them are axial and folding varieties. Prevent a drop in the working pressure in the system.
If there is no check valve at the end of the suction pipe of the pumping station, then when the pump stops, the water will begin to flow back by gravity. As a result, air congestion will form in the mains; in the conditions of a “dry run”, seals will break. As a result, water will penetrate the electric pump and cause it to burn out.
Not only the starting point of the suction line can be equipped with a check valve. To provide pressure support, it is installed on the pipeline in front of the pumping station or in front of the hydraulic tank when it is placed separately
Most modern pumps are protected against such processes. But the water for starting in them will have to be poured after each shutdown of the unit.
In some pump models, reverse impeller spinning is possible at all, which may lead to its failure. The installation of this valve on the line of fluid intake from the source is required, otherwise no electronic protection will help the water unit.
When connecting several pumping stations into a single unit, check valves protect the switched off unit from the pressure of operating devices
With a non-return valve, the situation is somewhat different. Here he protects not the pump, but the water distribution system inside the house. By locking the water in the pipes, preventing it from returning back to the accumulator, the check valve helps maintain the required working pressure in the system. Without it, water will tend back into the storage tank, forcing it to work in an emergency mode.
Check valves increase the efficiency and reliability of the pump station, while protecting the pump, plumbing and plumbing system from water hammer. In general - an indispensable device. But it takes a lot of effort to open the shutter to the water, which reduces the flow pressure after it passes by 0.1–0.3 atm.
Bottom check valve
Bottom types of check valves are installed at the inlet of the water pumping line. They are used to equip surface pumping systems to protect against pressure drop.
The task of the bottom check valve is to preserve water in the system and maintain the working pressure level (+)
According to the design specifics, bottom check valves are divided into:
- Spring loaded. Their working locking mechanism consists of a spring and a disk, which, when the spring is reduced under the pressure of the water, moves along the body of the device and passes the stream.
- Casement. The main organ is one or two transverse valves, opening under the pressure of the pumped water and returning to its place when it stops.
According to the method of fastening to the end of the suction hose or pipe, the bottom valves are divided into sleeve and flange. In tandem with household pumping units, the coupling type is most often used.
Under water pressure, the device spring is compressed, and the locking disk attached to it opens the flow path in only one direction
Couplings for check valves are easier to install, but require periodic status monitoring, especially when working with a vibration pump
Swing check valve is the easiest maintainable version of the device, the sash of which opens only in one direction under the pressure of pumped water (+)
A strainer is recommended in front of the bottom check valve. He must exclude the penetration into the pumping system of biological contaminants and particulate matter with an abrasive effect.
The device must be installed in the direction indicated by the arrow on the housing. The distance from the bottom of the water intake to the check valve should be at least 0.5 - 1.0 m, depending on the class of the unit and the manufacturer's recommendations. Between the water mirror in the well or well and the valve, there must be a water thickness of at least 0.3 m.
Pump systems with a submersible pump are equipped with a non-filter check valve, as they are equipped with built-in cleaning devices to protect the functional "filling" from friction. The non-return valve in this case is installed in front of the supply pipe immediately after the pump unit. Used to prevent pressure drop in the network.
The non-return valve in the pump system with a submersible pump is installed immediately after the unit at the inlet of the suction pipe
Pressure Support Check Valve
There are several designs of non-return valves for pipelines with a general principle of operation. All of them must provide unidirectional movement of the working fluid, for which they have a locking mechanism inside. It opens in the direction of flow, without obstructing it, and when you try to reverse the flow of water, it immediately closes.
With direct movement of water, the shutter element in the valve moves to the side, and with the reverse movement it closes the pipe tightly (+)
A conventional check valve consists of:
- housing;
- locking regulatory element (working body);
- springs (in some models it is absent).
The energy of the pressure of water flowing in the forward direction squeezes the locking element from the saddle, thereby creating a working window for the unhindered movement of the liquid. And when the current changes to the reverse, this shutter, under the action of the spring and water pressure, returns to its original place, blocking the pipeline.
Products of this type of pipe fittings are structurally different, used for stamping materials, as well as the method of fastening to pipes. At the same time, almost all types of check valves can be used when installing pumping stations, but this is not always practical and expedient.
Constructive varieties of products
The locking element can move in parallel, perpendicularly and at an angle to the axis of the pipeline. Most often, with dry pipes, it lowers into the saddle under its own weight. The device provides normal pressure in the water supply, preventing the reverse current supplied to the water intake.
Therefore, when mounting individual models of check valves, it is necessary to monitor not only the arrow of the direction of flow, but also the correct location of the cover, where the guide for the moving shut-off part is located.
Depending on the design, the valve inside the check valve moves, rotates or rises (+)
Internal constipation in the check valve can be made in the form of:
- a spool consisting of a stem and locking plates;
- whole or divided into two leaf discs;
- ball with a spring mechanism and gaskets.
In valves with a diameter of more than 400 mm, when the disc returns to the seat, it hits the body quite strongly, which inevitably leads to breakage of the device. To avoid premature wear of valves, these valves are equipped with hydraulic dampers, which make the drive stroke smooth.
However, such shock-proof check valves are not used in everyday life. There are simpler and cheaper analogues on sale.
If the check valve is needed in a small size, then the model should choose either a ball valve or a butterfly. In the first case, a small ball moves inside and back with the movement of water, and in the second case, the pipe is shut off due to two halves of the disk fixed to one rod. The case of both products is small-sized due to the lack of a moving spool inside with a wide spacing.
There are also non-return type constructions with forced opening / closing of the shutter. Flow control in this case is carried out by mechanical or manual devices. However, such back-stop valves are not used in everyday life with pumping stations. It is simply not needed for pumps.
Classification by type of mounting
In addition to the structural differences in the working element, the non-return valves used for installation with pumping stations differ in the method of fastening. The choice here depends on the material of the pipelines and the technology of their connection.
Spring-loaded check valve with a lifting spring mechanism consists of a brass body with a threaded thread (1, 2), a spool (3), a spring (4), a spool-lock plate (5) and gaskets (6)
According to the method of connecting with pipes, non-return valves are divided into:
- Coupling.
- Flanged.
- Wafer.
- Fatty (for welding).
The first type is connected to pipelines by means of a threaded transition, and the second is connected thanks to flanges with gaskets. Wafer type check valves do not have their own fasteners at all, they are fixed between the flanges of other water supply elements using long studs.
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Coupling check valve for water systems
Cast iron flanged check valve
Disc Type Inter Flange Valve
Weld check valve
The welding option is more suitable for use in pipelines through which aggressive media are pumped. With pumping stations they are not mounted. Wafer type check valves are available only in disc or double-leaf version.
For water supply systems, check valves with a lifting spring mechanism of closure and a coupling connection are most often selected. They are easier to mount and dismantle, as well as repair by replacing the spring, which is the weakest link in this pipe fitting.
Wafer products are small in size and quite high in price, they can be installed on pipes both horizontally and vertically
Material variation
The check valve body can be:
- bronze;
- brass;
- cast iron;
- stainless steel;
- plastic.
The most durable models are stainless steel, they are least susceptible to corrosion processes. From cast iron, non-return valves turn out to be bulky, so in everyday life they can rarely be found. They are mainly used on pipes with a large cross section. Such pipes are not connected to domestic pumping stations.
The most popular products are made of brass. This metal is relatively cheap, does not rust and is optimally suited to all types of pipes. Plastic products should be taken only for low-pressure pipelines and polypropylene pipelines.
The main breakdowns of check valves occur due to spring wear, it is worth choosing a product for the cottage with the possibility of replacing it with your own hands (+)
The working locking element is made of:
- stainless steel;
- aluminum;
- plastics.
In principle, all of these materials are equally good. The locking parts are small in size and are always made of high strength and durable. Failures most often occur in the spring mechanism. Therefore, the springs in the vast majority of models come from stainless steel, which is famous for its anti-corrosion characteristics and reliability.
In stores, you can also find combined check valves, the cases and covers of which are made of different materials. Each manufacturer seeks to reduce the cost of their products and offer the market some kind of novelty. Fortunately, all fittings are tested, you just need to require a certificate of conformity with the relevant norms and standards.
To achieve the valve tightness when lowering it into the saddle, rubber, plastic, and hard metal alloy hardfacings are used in various combinations.
Installation of valves with pump station
When choosing a non-return valve, it is necessary to take into account its nominal pressure, throughput and bore diameter. All these data are contained in the technical passport.
Installation can be done independently, following the instructions for the pumping station. In it, the manufacturer must indicate the recommended places for installing all the necessary fittings.
Installation option OK on a submersible centrifugal pump:
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Step 1 - selecting and checking the check valve
Step 2 - Determining the Right Installation Direction
Step 3 - screwing the valve onto the adapter thread
Step 4 - tightening with a gas wrench
The main thing here is to find out the presence / absence of a check valve in the pump station unit. If it is already a regular element of the water supply installation, then this reinforcement should not be installed additionally.
In this case, constipation will only reduce the capacity of the pipes, but there is no benefit from it. It is not worth spending money and time to install an unnecessary element, which will also create even small difficulties for the water flow.
Standard places for installing check valves are the lowermost point of the suction pipe and the inlet to the pressure line immediately after the pump station
If the water supply system scheme suggests the possibility of emptying the pressure line or the pump is operating in reverse mode, then the upper check valve cannot be installed after the water pressure unit. He simply will not allow such actions, blocking the flow of water to the water unit.
The sequence of installation of the “valve + gate” combination depends on the technology of starting the pump. There are models that were originally designed to run on a closed gate valve. In these cases, the check valve must be installed after the stopcock.
Manufacturers recommend installing backward lock in the “lower” position in all cases together with a coarse strainer.Water must first be cleaned of sand. The internal parts of the system will wear out faster from contact with abrasive particles.
It is better to immediately take back constipation with a removable or non-removable mesh. It will protect the device from sand, with it you will not have to install an additional filter.
Choosing the mounting point for the check valve, you must consider:
- water flow direction;
- availability of fittings for subsequent repair and maintenance;
- restrictions on strict horizontal or vertical installation of certain types of backward constipation;
- the presence of sand in the water, which can lead to clogging.
Spring-loaded check valves with a lifting shut-off element are least affected. The quickest and easiest way to install pipe fittings with wafer type connection. But more often, for water supply in private houses, inexpensive analogues with flange or coupling fastening are selected.
When using a submersible pump, a check valve is mounted on the end of the pipe lowered into the water intake, in front of the pumping device
When installing the check valve, it is important to install it correctly. The spool axis must be strictly vertical. And when installing a rotary product, the axis of rotation of the “flap” should always be higher than the center line of the water flow.
The direction of the flow of water and the correct location of the check valve allows the arrow on its body. It is difficult not to notice it, it is even more difficult to make a mistake with the locking device in the right position.
Video # 1. All about the technology of installing a check valve for water:
Video # 2. Overview of check valves for backflow blocking:
Video # 3. Which option of a non-return valve should be preferred for a cottage water supply system:
The use of check valves simplifies the operation of pumping stations and reduces the risk of accidents in the water supply system. Do not save on this small but important product.
Manufacturers now offer a mass of options for this valve of different sizes, the method of operation of the constipation and the type of fastening. For any water supply system and type of pump, it will be easy to find the optimal solution.
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