Air in hot water. Why does the hot water tap spit
Well for water - a convenient alternative autonomous water supply in the private sector. Having a number of advantages, the design requires not only proper installation, equipment with a filtration system, but also timely cleaning, as well as prevention and flushing. Due to non-fulfillment of at least one point, violations in the operation of the entire station are possible. For example, often water from a well comes with air. From the timely identification of causes and their elimination depends on the life of the pump, water quality and much more.
Cavitation as a reason
Before you begin clarifying the issue, it is important to know: the pumps are installed depending on the diameter of the well! For sizes of 100 mm suitable submersible pump, smaller diameter requires a circular or plunger pump.
What is cavitation? This is a violation of the continuity of the fluid flow, otherwise - the filling of water with bubbles. Cavitation occurs in areas where the pressure drop reaches a critical norm. The process is accompanied by the formation of voids in the stream, the release of bubble formations of air that appear due to vapors and gases released from the liquid. Being in the area of \u200b\u200breduced pressure, the bubbles can grow and collect in large hollow cavities, which are carried away by the fluid flow and, in the presence of high pressure, are destroyed without a trace, and in a normal household well, it often remains and it turns out that the pump pumps air bubbles from wells without giving out the right amount of water.
Identification of the cavitation zone is sometimes impossible due to the lack of special devices, but it is important to know that such a zone can be unstable. If the defect is not eliminated, then the consequences can be devastating: vibration, dynamic effects on the flow - all this leads to a breakdown of the pumps, because each device is characterized by a specified value of the cavitation reserve. Otherwise, the pump has a minimum pressure, within which the water entering the device retains the density properties. With changes in pressure, cavities and air voids are inevitable. Therefore, the selection of the pump should be carried out depending on the volume of water needed to provide household and household needs.
The destruction of air bubbles occurs only when they are transported by a stream to an area of \u200b\u200bhigh pressure, which is accompanied by small hydraulic shocks. The frequency of strokes leads to the appearance of a hissing sound, by which it is possible to determine the presence of air in the well.
Cavitation Elimination
What can be done to avoid the appearance of air in the well and the flow of water with bubbles:
- Replacing a small diameter suction pipe with a larger one;
- Moving the pump closer to the storage tank.
Attention! When moving the pump, observe the established standards: the distance from the pump to the tank must not be less than 5 diameters of the suction pipe!
- Reduce the pressure of the suction element by replacing it with a smooth pipe, and the valve can be replaced with a gate valve, and the check valve can be completely removed;
- The presence of a large number of turns in the suction pipe is unacceptable, they must be reduced or replace bends of a small radius of turns with large ones. It is easiest to orient all bends in one plane, and sometimes it is easier to replace rigid pipes with flexible pipes.
If all else fails, you will have to increase the pressure on the suction side of the pump, raising the level of the tank, lowering the axis of the pump, or connecting the booster pump.
Note that all the manipulations are shown based on a large volume of water consumption and the installation of powerful pumping devices. And, it is important that cavitation can occur only at a depth below 8 meters. It is with such a length of all elements and the presence of high pressure in pipes, the liquid goes into a gaseous state and the water flows with air.
Other causes of air bubbles in the well and methods for eliminating them
When using a well to pump out small volumes of water or seasonal operation of a structure, several possible causes and ways to eliminate them are possible. So, why the pump pumps not only water, but also air:
- Air leaks in the suction section. At the same time, water and air flow for a long time, but the problem is "cured" only by a complete replacement of the pipeline and all associated elements. You can check by removing the pipeline from the well and pumping water, for example, in the bathroom.
- Low filling of the aquifer with a large pumping. Reducing volumes or punching a new well will be the best solution. It is only important not to break through to the former skinny aquifer so as not to get water and air from the well again.
- Damage to the pump when the stuffing box packing is unstable, as a result of which air bubbles are in the discharge chamber and water comes with air. You will have to disassemble the device yourself or it is easier to give it to a repair shop.
Hydraulic systems are akin to electric ones - the laws are the same here. Sort out the problem why pumping station pumps air, sometimes it is possible only with a series of technical measures. And if the proposed options for identifying the problem and eliminating the deficiencies did not help and the water also comes with air, it is better to contact the professionals who service the pumps. The cost of the service is from $ 50, but you will be spared the problem and you can find out exactly why your pump does not pump water as you would like.
Water pipes are designed to transport water, so there is no place for air here. However, air enters the pipes. Why is this happening and what is the danger of air in the water supply systems of private houses? Is it possible to prevent its penetration and how to remove air from the water supply system?
What is the danger of air in the water supply
Why does air appear in the water supply
There are two reasons for the appearance of air in the home's water supply system:
- Outside. Air leaks through pipes through leaks;
- From the inside. In a stream of water passing through the pipes, approximately 30 grams of air per 1 ton of water are dissolved. Gradually, air is released. The slower the water flows, and the hotter it is, the faster the process. That is, in hot water systems, the likelihood of air congestion is higher.
In the water supply systems of private houses, air appears for the following reasons:
- when the water level drops, air can suck through the check valve;
- poorly tightened fittings with rubber seals;
- cavitation is observed in hot water supply systems: steam forms, air bubbles collect in the water, forming voids or caverns;
- the air in the water pipes remained from the first start of the equipment.
In air bubbles, oxygen is 30% more than in atmospheric air. This explains the high oxidizing ability of air in hot water systems. Air bubbles can be of various shapes: spherical - small, not more than 1 millimeter in diameter, mushroom-shaped, oval.
In vertical pipes, bubbles rush up or are distributed throughout the volume. In horizontal highways, they stop at the highest points where they conduct destructive work.
When the water velocity in the pipes is more than 0.5 meters per second, the bubbles move without stopping. When the speed exceeds 1 meter per second, the bubbles break into very small bubbles. It looks like an emulsion of water and air. Air bubbles in the water supply system of a private house begin to collapse at a fluid velocity of 0.25 meters per second. If it is lower, traffic jams can stagnate in some places for a long time.
How to get rid of air in pipes
If there is already air in the water supply system of a private house, but it is not equipped with vents, it is necessary:
- Turn off the pumping station.
- Open all drain taps, discharge water and air from the water supply system. Then the pipes are filled again.
You can remove air from the water supply system once and for all with the help of bleed or drain devices:
- mechanical valves such as the Majewski valve;
- automatic air vents;
- ball valves;
- gates.
Mechanical valve device for venting from the water supply system is as follows: a cylindrical box, closed with a lid on top, a thread on the bottom for connection to the water supply. In the middle of the cover is a cap on the thread. A ball-shaped plastic float is suspended inside the cylinder. If there is no air in the hot water system, the ball rises to the hole in the plug and closes it tightly under pressure from the network. As soon as air enters the device, the ball leaves and air is discharged. Air can enter the system through venting devices, which is useful when repairing or inspecting networks and speeds up water drainage.
Air-removing devices are installed in certain places of the water supply system: in the uppermost extremities, at bends or kinks. That is, where the likelihood of air accumulation is increased.
Homemade air storage
In rural water pipelines, air often flows mixed with water. Using such a water supply is difficult and inconvenient, and automation does not always cope: if there is a lot of air, water flows over a fountain directly from the valve. Therefore, instead of an automatic venting device for air discharge in the water supply system, air accumulator. It can be done independently; it is a tank with a branch pipe and a tap. The diameter of the drive should be 5 times the diameter of the water pipe, then it can work efficiently.
An air accumulator is installed at the highest point in the water supply system where it is convenient to bleed air by hand. Air storage tanks are widely used in multi-storey buildings in hot water systems.
Automatic air vents
Devices for removing air from plumbing systems are widely marketed. Float valves this continuous air vents. They protect the working system from the accumulation of air and gases. When the pressure in the system drops to atmospheric, the float valve lets air into the pipes. To eliminate the cause of the appearance of air in the water supply system of the house, an optional check valve is installed. There are air vent models already equipped with a non-return valve.
Start-up air vents They are used to remove air while filling the system with water or to start air during drainage operations.
Combined air vents possess the properties of both devices described above.
When choosing an air vent, the volume of exhaust air is taken into account. This indicator can be found in the characteristics of the device. Do not pick up an automatic air vent more powerful. Working half-heartedly, it will wear out faster.
For the correct operation of the air vent, the working pressure in the water supply and the quality of the liquid are important. If the resource density is below 960 kilograms per cubic meter, special design floats are installed.
A video clip about the simplest air vent - the Majewski valve:
Good afternoon. I want to understand the reason for the malfunction of the water supply in the country.
From the well, water is pumped into the house. In the house, a check valve is in front of the hydraulic tank. After the hydraulic tank the filter and then the water heater. Next is the sink. When I open the faucet with cold water, the water flows evenly, and if you open the hot water as well, at first it flows well and a few seconds later it starts to “spit” a little. Somewhere it draws in air .. There is no leak, the pressure in the system does not drop !! How to solve the issue ??
Help advice, please .. Yuri
Hello, Yuri.
It’s a pity, you didn’t indicate what kind of “hydraulic tank” you have installed - a membrane freestanding, as part of a water supply station or an open one. It is also not known what type of water heater you are using: electric storage, electric flow or gas. And what is “starting to spit a little”? “A little bit” is how? Since you decided not to pamper our experts with an abundance of information about the features of your cold and hot water supply system, it is not a fact that our answer, based on fragmentary data, will satisfy you. Let's try the logical way:
- If the "hydraulic tank" is a closed membrane tank, air leakage cannot occur in the area where there is high pressure. If there were leaks, it would not be a leak, but rather a leak. The area where air can enter the system is the supply hose if you have a surface pump installed. Theoretically, the submersible pump can also catch air if the water mirror periodically drops to the level of water intake. Protective automation shuts off the pump before the system is airy, the level rises again. It is unlikely that everything coincides so precisely, but it cannot be ruled out. However, in case of suction, air would also get into cold water. So, this is hardly the reason. Unless an air trap is installed in the cold water line.
- Air can enter the pipes if the check valve installed in front of the “hydraulic tank” does not hold. The water in the hose flows under its own weight into the well, negative pressure forms and somewhere (for example, in an open mixer) air is trapped. The probability of this is small, but still.
- Air can enter the hot water supply if you do not have a membrane tank installed, but an open storage tank. The pressure is low, the connection to the water heater is separate and somewhere on the way to it there is a leak in the pipe. It can also “jump” the level in an open tank, if the filling valve does not always work.
- If air does not penetrate the system from the outside, then it forms inside. Water from the well contains dissolved oxygen and other gases. When heated, they stand out in the form of bubbles. In this case, the liquid does not have to boil, the transition of oxygen from the dissolved to the gaseous state occurs at a temperature slightly above room temperature, an intensive process begins at 50-60 ºС. The higher the temperature, the more actively gas formation occurs. If you have a storage water heater installed, air can accumulate in the upper part of the heating process.
In the upper part of the water heater there is a space where the hot water extraction pipe does not reach. Under certain conditions, a dozen liters of compressed air can accumulate there, which causes the mixer to “spit” for some time after opening the hot water tap
The amount of air will be greater if the water heater is installed at the top point of the water supply. Another reason that increases the rate of gas accumulation is the incorrect operation of the automatic heating of the storage electric boiler against the background of a malfunction of the boiler safety valve. By the way, if tap water has a high carbonate hardness, after two or three years the valve “overgrows” with salt deposits. There is water in the pipe going to the mixer. After opening the hot water valve, it drains, the system captures the water, the tap “spits”. If such a phenomenon occurs after you have not used hot water for some time and after a couple of minutes the flow is restored - we are on the right track. Another sign is too hot water. Disconnect the boiler from the power supply and try to spill unheated water. There is no air - that means the reason why the tap "spits" is installed.
What to do? First, replace the safety valve and lower the heating temperature. It didn’t help - to install a dehumidifier at the top point of the system, preferably placing it on a U-shaped branch (jumper), where gases can accumulate without blocking the flow.
An automatic air conditioner costs more than usual, but saves time and nerves
- If the mixer “spits” constantly, check the aerator, just unscrew it from the spout.
- Some filters, more precisely, water treatment systems, can aerate water. The simplest mesh filters are not capable of this, but if the installation is complicated, try to bypass the water for a while or at least remove the cartridges.
- It is possible the evolution of gases during an electrochemical reaction. This may be due to direct contact of various metals, for example, copper and aluminum. Metal fittings should be connected through rubber gaskets, FUM tape, tow.
The correct installation diagram of the electric storage water heater. Do you have a safety and non-return valve installed?
