Contents
In order for modern household appliances to work, there was a normal pressure in the faucet and shower, it is necessary to create a certain level of pressure in the water supply system. One of the components that is responsible for this is the check valve for water. What is this device, how does it work, where to put it. Read on for this and more.
What is a check valve for water, its purpose and scope
Check valve is one of the types of valves. The essence of his work is to block the movement of the flow in the opposite direction. Its second task is to prevent pressure drop.
With regard to the water supply, it blocks the reverse movement of water. In private water supply systems (from wells or wells), the check valve is set so that after the pump is turned off, it retains water in the suction pipe. If the system is made on the basis of a pumping station, then most likely it contains a check valve. But this must be seen in the passport. Is the second necessary or not in this case? Depends on the length of the supply line, the section of the pipeline, the performance of the pump and several other factors. But more often they put it on.
In apartments or with central water supply in the house, it is placed in front of the meter. But here his task is different – to prevent the possibility of “rewinding” testimony. The presence or absence of a check valve in this case does not affect performance. But its installation is a prerequisite for the operational organization. The seal is placed so as not to exclude unauthorized analysis of water.
Where else can a check valve for water be required? In the heating system. Not centralized, but private. It may contain circuits in which, under certain conditions, a reverse flow may occur. A non-return valve is also installed on such circuits. In the boiler piping, in the presence of a hygienic shower. These devices can also reverse flow. So a shut-off valve is needed.
Types of check valves, its device and principle of operation
The check valve is simple. There is a saddle with some narrowing and a locking element. With the “correct” flow, the locking element is pushed away from the bottleneck. As soon as the direction changes, it presses against the saddle, blocking the passage. By the way, there should be an arrow on the body that indicates the “correct” direction of water movement.
Basically, check valves are distinguished by the type of shut-off element. He can be:
- ball type (ball);
- poppet;
- disk;
- petal or bivalve.
In a ball valve, the ball is “free floating”. It is not attached to anything, it is carried by water. A completely reliable system. But it does not always cover the saddle tightly enough, so it is used quite rarely.
Dish-shaped can be lifting or rotary. Swivel, as well as ball, open and close under the influence of water flow. Lifting have a spring-loaded stem. In the “normal position” the passage is closed, when water pressure appears, it depresses the spring, pushing the locking element upwards.
The most common in domestic water supply systems is a disc check valve. It differs in that the fittings of this type can be small in size. And the design is simple and reliable. The locking disc is placed across the flow, it is pressed against the seat by a spring. The water compresses the spring, freeing its way.
There is also a bi-fold valve for water. Its locking element consists of two halves of the disk (petals), which are fixed on the axis. Hence another name for this model – petal. They are held closed by springs. Water entering the plumbing presses them back, folding and pressing against each other. This type provides the least hydraulic resistance. In some cases (with long suction lines) this may be important.
Materials, markings, dimensions
The check valve for water is made of stainless steel, brass, large sizes of cast iron. For household networks, they usually take brass – not too expensive and durable. Stainless steel is certainly better, but it is usually not the body that fails, but the locking element. That’s his choice and should be approached carefully.
For plastic plumbing systems, check valves are made from the same material. They are polypropylene, plastic (for HDPE and PVD). The latter can be welded / glued or threaded. You can, of course, solder adapters to brass, put a brass valve, then again an adapter from brass to PPR or plastic. But such a node is more expensive. And the more connection points, the lower the reliability of the system.
The material of the locking element is brass, stainless steel or plastic. Here, by the way, it’s hard to say which is better. Steel and brass are more durable, but if a grain of sand gets between the edge of the disc and the body, the valve jams and it is not always possible to return it to work. Plastic wears out faster, but it does not wedge. In this regard, it is more reliable. No wonder some manufacturers of pumping stations put check valves with plastic discs. And as a rule, everything works for 5-8 years without failures. Then the check valve begins to “poison” and it is changed.
What is indicated in the label
A few words about the marking of the check valve. It states:
- A type
- Conditional pass
- Nominal pressure
- GOST according to which it is made. For Russia, this is GOST 27477-87, but not only domestic products are on the market.
Check valve for water: marking according to GOST
Conditional pass is designated as DU or DN. When choosing this parameter, it is necessary to focus on other fittings or the diameter of the pipeline. They must match. For example, you will install a water check valve after a submersible pump, and a filter to it. All three components must have the same nominal size. For example, all should be written DN 32 or DN 32.
A few words about conditional pressure. This is the pressure in the system at which the valves remain operational. You need to take it exactly no less than your working pressure. In the case of apartments – no less than a test one. According to the standard, it exceeds the working one by 50%, and in real conditions it can be much higher. The pressure for your home can be obtained from the management company or plumbers.
What else to pay attention to
Each product must come with a passport or description. It indicates the temperature of the working environment. Not all valves can work with hot water or in a heating system. In addition, it indicates in what position they can work. Some should only stand horizontally, others only vertically. There are also universal ones, for example, disk ones. Therefore, they are popular.
The opening pressure characterizes the “sensitivity” of the valve. For private networks, it rarely matters. Unless on the supply lines close to the critical length.
Also pay attention to the connecting thread – it can be internal or external. Choose based on ease of installation. Do not forget about the arrow that indicates the direction of water movement.
Dimensions of check valves for water
The size of the check valve for water is calculated according to the nominal bore and they are released for everything – even the smallest or largest diameters of pipelines. The smallest is DN 10 (10 mm nominal bore), the largest is DN 400. They are of the same size as all other shutoff valves: taps, valves, spurs, etc. Another “size” can be attributed conditional pressure. The lowest is 0,25 MPa, the highest is 250 MPa.
This does not mean that any of the valves will be in any variant. The most popular sizes are up to DN 40. Then there are the main ones, and they are usually purchased by enterprises. You won’t find them in retail stores.
And yet, please note that for different companies with the same conditional passage, the external dimensions of the device may differ. The length is understandable. Here the chamber in which the locking plate is located can be larger or smaller. The chamber diameters also differ. But the difference in the area of the connecting thread can only be due to the wall thickness. For private houses, this is not so scary. Here the maximum working pressure is 4-6 atm. And for high-rise buildings it can be critical.
How to check
The easiest way to test a check valve is to blow into it in the direction that is blocking it. Air must not pass. At all. No way. Also try pressing the plate. The rod should move smoothly. No clicks, friction, distortions.
Also inspect the seat and disc. Especially where they are next to each other. Everything should be even/smooth. The tightness of this type of fitting depends on how accurately everything is fitted. In more expensive models, a rubber / polymer / plastic o-ring is installed on the plate. Needless to say, it should lie flat, without waves, there should be no scratches or burrs.
Where to put the check valve
To begin with, a few words about how the check valve for water is indicated on the diagrams. There is a special icon for it. These are two triangles with their vertices facing each other. One of the triangles is shaded, one is not. The direction of movement of the working medium is indicated by an arrow. In the opposite direction, the flow is closed.
In general, there is no clear indication of where exactly the check valve should be placed. It is important that it performs its functions, and the place of its installation is a secondary matter. It is necessary that the water supply or heating system works correctly. And its specific place is determined by the parameters of the system and by ease of maintenance. The exception is the water supply in the apartment. Here they will clearly tell you, we put the check valve in front of the counter and nothing else.
For example, in the boiler piping on the supply pipe, there must be a check (shut-off) valve. It prevents hot water from entering the system, which can occur when the water heats up and thereby creates an increased pressure that can “transfer” the plumbing. In this case, it is better to place the return valve closer to the source of hot water so as not to expose other piping elements and cold water pipes, which are far from always made of metal today.
On a well or in a well with a submersible pump
If you look for information on where to put a check valve on a submersible pump, the information may be contradictory. Some advise putting it right at the pump outlet, others – at the entrance to the house or in the pit, if we are talking about a well. Oddly enough, all three options work. Just for different occasions.
It is possible to put a check valve in the house or in the pit above the well if the vertical section of the pipeline does not exceed 7 meters. The length of the horizontal section (if it is without slope) does not play a role. With such a length of the pipeline, water will not flow back into the well or well.
If the water surface is below seven meters (the pump draws water from a depth of more than 7 meters), we put a check valve after the pump. You can immediately (as in the photo above), or you can put a filter, then a check valve. It is permissible to install the valve a couple of meters above the water level. It no longer plays a big role. But this method of installation – at a depth – is inconvenient for maintenance. Sooner or later, the valve will either have to be cleaned or replaced. If it is in a well or in a well, everything must be taken out to the surface. The replacement itself takes a matter of minutes. It takes about five minutes to unscrew the thread, remove the old one, check / clean or put in a new one. But all the preparatory work is hard, wet and unpleasant. So, if possible, we transfer the check valve to the house or pit.
with pumping station
As already mentioned, some models of pumping stations have a check valve. Should I put a second one on the suction pipe? Again, if the water rises less than 7 meters, you can do without it or put it at the entrance to the house.
If the vertical rise is greater, it should be set at the entrance. For what? And because when the pump is turned off, the water will flow back. And when turned on, it will pump air, and only then water. And let’s say right away that not all stations normally tolerate such a regime. Therefore, if you hear that the water returns to the well or well after the pump is turned off, it is better to redo the system.
As you can see, in this scheme, a check valve is installed at the end of the pipe. Since it is sensitive to pollution, it is better to clean the water first. You can wind standard filters, or you can put it with a built-in mesh. Which option is better? Probably the first one anyway. First, you can collect as many filters as you need in series to supply relatively purified water. Secondly, it is cheaper to change one filter or one valve than a filter with a valve. There is more fuss during installation, but not critical.
Why is the valve not working?
A sign that the check valve has broken is that the system cannot hold the accumulated pressure. Rather, a broken valve is only one of the reasons. The second is the leakage of the supply pipeline. So you have to check both options.
If you look carefully at the check valve device, you will understand that there is nothing to break. Possible breakdowns are a wedge on the rod and debris that prevents the disk from being pressed tightly. It could also be the wear of the locking plate. The latter is incurable, we immediately change it. Wear is the pressed grooves from the seat on the sealing ring too. So the presence of a seal is an ambiguous advantage. Rubber is pressed through and the valve begins to “poison”.
If the stem is slanted or jammed, in some cases it can be corrected. It usually doesn’t last long, and it will jam again pretty soon. If the striker plate has become clogged, it can usually be cleaned. And so that this situation does not recur, put a filter in front of the check valve. If it is already there, and the water is still too dirty, there are several options:
- put the second – smaller filter;
- either raise the end of the pipeline from the bottom level;
- clean or deepen the well or well.
If we are talking about a submersible pump of the “Kid“ type, damping the vibrations that occur during its operation will help reduce the amount of turbidity. The methods are different – from the use of springs in the suspension, to the rubberized suspension. It really helps. Another option is to put a barrel with a wide neck into the well at the bottom, and a pump into it. Silt and sand will rise less.
Next note. If, after a long period of operation without failure, the non-return valves begin to “fly” one after another, the water level may have changed and you need to move the suction point. The second option is that the pipes are clogged with sand or silt and it is necessary to simply flush the pipeline. Well, check it for leaks. By the way, if the station is not gaining pressure, then the point is most likely not in the check valve, but in the bulb, its mount, nipple, etc.