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Plumbing in the Home/water getting sucked out of system when pump is turned off?

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QUESTION: HI!  We have a vacation house and we began turning the water pump off (but leaving the heat on, set at 45 degrees) when we leave the house, so that if there were a water disaster there would be a limited amount of damage.  WE have an on-demand, hot-water (old fashioned) radiator system, with old radiators, the house is new construction, the plumbing system is new - seven years old.  At first, we would come back and there would be water in the pipes, you would turn on the sink or flush the toilet, and there would be water in the system, even before we turned the water pump back on.  After a while, we found that no water was left in the pipes, nothing would come out until the pump was turned on.  And then when we were away last time, the temperature alarm went off, and the temperature dropped in the house, and it appeared that the on-demand heater had stopped, because the water pressure had dropped.  When we turned the water pump back on the pressure went back up and the heat eventually came on.  Why would the water back out of the system like this (there are no leaks -- inside the house anyway), and, does this mean we are never going to be able to turn the pump off again?  We have an "iron-filter" water filtration system, a pressure tank that is rather big for a 1500 square foot house...and those are about the only other relevant things I can think to tell you.  Thanks!

ANSWER: Getting ready to go out to eat so I have to make this short :0  Every well system has a pressure tank.  A place to store well water.  Even with the pump off, this take being full will continue to supply pressured water for about 30 seconds to a couple mins, depending on the size of the tank AND at what point you shut off the pump. In other words, you could have shut off the pump BEFORE it filled the tank.  Or you could of had a full tank and flushed the toilet a few times and so the tank was almost empty but not empty enough for the pump to kick on.  So if you shut down the pump with a full tank, it will last a little while.  If you shut it off when it was almost empty, then it could gradually leak back into the well, thus the alarm.

So it's a bit complicated.  Before you leave, run water inside the house until you hear the pump kick on.  Then shut off the water and stay until you hear it cut off.  Then DO NOT run any water anywhere and turn pump off.  Now you have a full tank, still limited to prevent flooding, while hopefully, not runniing out to set off any alarms.

Make sense now?  :)

---------- FOLLOW-UP ----------

QUESTION: Yes, everything except, I thought the heating circulators were some sort of closed system, where water is not needed to be supplied all the time, I thought it kept using the same water!  I guess that is not correct.  Thank you for your helpful response, and your time.

Answer
Well, you're getting into two diff trades.  I am not an expert on your heating unit / coils and not qualified to answer.  But anything related to the rest of your question, I'm your man :)

Remember that you could have a VERY small leak, like a bad check valve or a foot valve (have no idea what kind of pump set up you have, submersible or exposed jet pump) and under everday normal usage, not bad enough to cause a backflow problem.  However, when gone for long periods of time, this small, not really troublesome leak, can gradually let water drain back into the well, thus emptying the system of water.

Plumbing in the Home

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