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BUILDER, HOUSEHOLDER
Freezing plumbing. Tips for the home master
Directory / Builder, home master I would like to share my experience of building a winter water pipeline for a periodically heated garden (country) house. The operation of my water pipeline in the winter of 2012/13, when the temperature dropped to minus 35 ° C, showed its high reliability. The plumbing scheme is shown in fig. 2. Water pipes are laid at a depth of only 30 - 40 cm, but do not require heating. The level of penetration is determined by considerations of labor costs and the creation of a minimum slope (approximately 2 cm per meter of pipe) in the direction from the house to the well. The operation of the water supply system is based on the principle of "dry pipes", which means that when the pump is not working, the supply pipes from the surface of the water in the well to the point of connection of the check valve, which is located indoors (Fig. 2, point A), are always without water, that is, they are "dry". Let's consider the water supply system shown in the diagram (Fig. 2). Water from well 1 is supplied by pump 3 through flexible hose 2, pipe 4, check valve 5 to hydraulic accumulator 12 and from it to consumers (in the figure this is sink tap 11). In addition, water tends to fill receiver 7, which is connected at the inlet of the check valve. The circuit for monitoring water pressure in the water supply system and controlling the pump consists of a pressure gauge 9 and a pressure switch 10. When the pump is first turned on, water moving through the pipes compresses the air in the pipes. This air tends to enter the receiver and accumulator. In the cavity of the hydraulic accumulator, such an air pressure is preliminarily created, which prevents the filling of the hydraulic accumulator with air coming from the pipe, and then with water, until the receiver is filled with air. After the receiver is filled with air, water begins to flow into it, compressing the air in it, and the flow of air and water into the accumulator also begins. When the required pressure in the accumulator is reached, which is determined by the required water supply in it, the pressure switch will turn off the pump. As soon as the pump turns off, the compressed air from the receiver will push the water out of the pipes into the well. In this case, water and air behind the check valve will remain in the accumulator and pipes. After several analyzes of water, the air from the accumulator is vented into the atmosphere. The next time the pump is turned on, the operation of the water supply to point A will remain the same as described above, and after point A, only water (without air) will be pumped into the accumulator. Tap 6 is used to drain water from the system, bypassing the check valve. In this case, it is necessary to open the taps of all consumers. During long-term operation of the water supply system, the amount of air in the main line to point A may decrease due to its absorption by water, which will lead to incomplete expulsion of water from the pipes. Therefore, periodically, approximately once every four to five days, it is necessary to open tap 8 with the pump not running to completely remove water from the receiver. To prevent the pump from turning on, it is advisable to place an additional power switch for the pump next to tap 8.
Consider the operation of the water supply system using a specific example (Fig. 2): the distance from the house to the well is 10 meters; the maximum distance from the point of connection of the flexible hose to the pipe to the surface of the water is 3 meters; the pipes and hose leading to the house have an inner diameter of 16 mm. Let us determine the minimum volume of the receiver \/Pmin. The maximum air volume in the hose and pipes up to the check valve \ / in is determined by the well-known formula: Vв = (πD2/4)L, (1), where D is the inner diameter of the hose and pipe, L is the distance from the water surface to the check valve (10 + 3) x102 (cm - for ease of calculation). In this way, Vв=0,8x1,62x13x102cm3≈2,6x103 (cm3, or approximately 2,6 liters). Therefore, the volume of the receiver must be more than 2,6 liters. Two series-connected housings from “Aquaphor” filters (or “Geyser” filters) without cartridges were used as a receiver. In this case, the volume of the receiver is approximately three liters. Let us determine the minimum value of the pre-created pressure in the hydraulic accumulator RAmin. As noted earlier, this pressure must be greater than the minimum pressure in the receiver PPmin, created when air is completely displaced from the hose and pipes, i.e.: RAMin ≈ PPmin (2). It is known that the product of gas pressure and its volume in a closed space is a constant value, i.e. VxP = CONST(3). Therefore: 5,6x1 \u3d XNUMXxPPmin, where: 5,6 l (3 + 2,6) - the total volume of air in the receiver and in the pipes before compression, 3 l - the volume of compressed air in the receiver without water. Thus, PPmin ≈1,6 atm. Taking into account (2), we take PPmin ≈ 1,8 atm. 3. Determine the nominal pressure in the accumulator PANom. RAN is the pressure at which the required volume of water is pumped into the accumulator (for example, 2 liters). We use an industrial accumulator with a volume of VA = 8 liters. From formula (3) it follows: PPminx8= RAminx6, where 6 is the volume of air in the accumulator after pumping two liters of water into it. Thus, RAN ≈ 2,4 atm., Let us take RAN ≈ 2,6 atm. So, having calculated the values of RAMin and RANom, we determined the threshold values for the response of the pressure sensor. The pressure at which the pump turns off should be 2,6 atm, and to turn on the pump - 1,8 atm. Consequently, the hysteresis of the pressure setting is Δ = 0,8 atm. The settings of the pressure sensor are carried out according to the factory instructions for it, while control is carried out using pressure gauge 9 (Fig. 2). From the above calculations it follows that in this water supply it is necessary to use a pump capable of creating a water pressure of more than 2,6 atm. Such pumps can be, for example, “Aquarius” or “Rucheek”, capable of raising water to a height of 30 meters and above. With a greater distance from the well to the house and a larger diameter of the supply pipes (unlike those considered), it is obvious that the volume of air in the pipes will increase, therefore, it is necessary to increase the volume of the receiver. Next, consider some of the design features of my plumbing. To prevent freezing of the upper layer of water in the well, and hence the formation of an ice plug in the hose, the well shaft is insulated from the ground surface to the head with two layers of polyethylene foam 8 mm thick (Fig. 1). The upper part of the head is covered with foam plastic 50 mm thick. The introduction of pipes into the house and other structural elements are shown in fig. 3.
Approximate dimensions of the flange are shown in fig. 3. The hose elbow was made in the following way: the fitting 1 was heated to a temperature of ≈ 150°C, after which the threaded part was fused into the elbow 2. The polypropylene parts were soldered together. The pipes from the well to the entrance to the heated room of the house are insulated with standard foamed tubular insulation and placed in polyethylene sewer pipes with a diameter of 110 mm. In addition, for ease of installation, the flange is placed in a pit lined with bricks and closed with a wooden cover. The plumbing in the house is also made with polypropylene pipes with a diameter of 0,5 ". Cranes 6 and 8 are ball valves. When installing in the house of various consumers, flexible connections were used. At the same time, special attention was paid to preventing the formation of so-called "siphons" that prevent the guaranteed discharge of water from the piping when the water supply is turned off. For insurance in case of unexpected freezing of the supply pipes, I used a self-regulating heating cable from a 150 W underfloor heating. The cable is attached to the pipes inside the thermal insulation with aluminum tape and can be turned on manually in case of an emergency. However, for a year and a half of operation, such a need did not arise. Author: V.Ivanov
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