Problem with water system

[naiad]

This morning got up no water......pulled pump out of 90 foot well repaired damaged wire. Put pump back in well.......now can't get water to fill pressure tank.......it seems to be sucking the water out of hot water tank....we also have a water system. Please help!!! We pulled the pump again and found a hole in the piece that connects the pump to the pipe.......Now the pressure tank won't kick on........when we hold the pressure switch up water is that is moving is hot, which we have decided that the hot water tank is draining this is very strange.................please help!!! All Fixed

[LazyPup]

The problem is a defective check valve at the well pump.

I have prepared an attached illustration that will help you visualize the problem.

While we generally only think in terms of PSI (pounds per square inch) that is really an incomplete statement. In plumbing all pressure readings are measured in PSIG (pounds per square inch-guage). We must remember that the earths atmospher has an average pressure of 14.2psi at sea level therefore a PSIA guage would read 14.2psi at sea level when no pressure other than air pressure is present such as if you were holding the guage loose in your hand. Theoretically zero PSIA would be a perfect vacuum. For the purposes of pumping fluids it would be a bit confusing to continually subtract atmospheric pressure from a guage reading to determine the actual pressure on the fluid. For this reason we have PSIG guages that read zero at standard atmosphere and only display pressure above standard atmosphere. (In the refrigeration trade they use a compound guage which is a PSIA guage that is calibrated to display zero at standard atmospheric pressure and PSIG above standard atmosphere but for pressures below standard atmosphere it is calibrated in Inches of Mercury (In/Hg) thus when they pull a vacuum on your AC they want to pull it down to 32In/Hg which would be zero PSIA or a perfect vacuum.

Under the International Residential Code the minimum allowable static head pressure at the main is 40psig which is commonly used as the "Cut in" pressure on your pressure tank (The pressure where the pump starts). We then set the Cut Out or stop pressure at 60psig.

This means that we want the pressure to be 40psi above atmosphere at the pressure tank but the pump is at the bottom of a 90foot well. Keep in mind that the physically weight of water is .434pounds per vertical foot which means the pump must first overcome the phyiscal weight of the water it is lifting before it can begin genrating additional presssure. The physical weight of the vertical column of water is properly called "Vertical static Head" and when pumping vertically it must be thought of as a resistance.

Now for the moment let us assume the point where the pressure sensor is mounted on the Pressure tank is ten feet above grade while the pump is 90' bleow grade so the total vertical static head is (90'+10')x.434= 43.4psi. Thus the pump at the bottom of the well must exert 43.4psig just to get water to the tank but the water in the tank would only be at standard atmospheric pressure. WE desire the operating pressure of the system to be a minimum of 40psig so the pump must exert 43.4+40 =83.4psig to produce the desired result.

We must also understand that the surface of the water in the bottom of the well is at standard atmospheric pressure therefore once the pump turn off the vertical column of water has a 43.4psig downward pressure which would quickly backflow the water through the pump and back to the well. To prevent that from happening they put a Backflow preventer (check valve) on top of the pump.

Anyone who has ever played with a soda straw knows that you can put the straw in a glass of liquid and hold your finger on top of the straw and the liquid will stay inside the straw until you remove your finger. The same thing happens in a well pipe. When the pipe is full and all valves and faucetts are closed the water remains in the pipe, at least for a fairly long time but it will eventually go down nonetheless, however, if the pump is off and the check valve at the bottom of the well is not sealing then you open a faucett air vents into the pipes through the faucett just as if you removed your finger from the straw. When this happens the vertical static head in the pipe causes an immediate downflow of water which will then cause the water in the pipes in your house to backflow by syphon action. The hot water in your water heater is then syphoned out of the heater through the cold water "Dip Tube" and the syphon action will continue until the water level in the tank reaches the bottom of the Dip tube. When this occurs air will then get into the water portion of the pressure tank as well as the line to the well and down to the pump. If you were to then close the faucett and run the pump the air in the line is pushed upwards by the rising water even though the air is compressible, it will eventually be compressed enough to switch the pump off even though no water has yet arrived at the pressure tank.

In this case there is also the strong probability that you got air in the line during your maintenance procedure.

You should immediately turn off the water heater elements or burner to protect the tank from burning out until you are certain it is properly filled with water again.

Open a faucett to bleed excess air and try manually tripping the pump control to turn the pump on until you have water flow at the faucett and the pump will stay on by itself. Expect a lot of sputtering and spitting from the faucett until the air is out of the system. Also expect air, followed by a full stream of water, which is any water remaining in the pressure tank and water heater followed by a second segement of air. Once you have full flow again you should be ok. If the pump then looses its prime again you will need to pull the pump and replace the check valve.