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Suspected leak in slab

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  • Suspected leak in slab

    I have been helping a small church with a problem and need some advice. We suspected a leak in a copper hot water line in the slab. I put a gauge on the hose bib at the mop sink , opened the valve and closed the input valve to the hot water heater. The pressure drops (about 4psi over two hours) but comes back up later (quite a bit, almost double). I expect this to be caused by cooling and heating in the tank. Should I turn off the heater for a while and run the test and if so how long?

  • #2
    Bob: The easiest and cheapest way to check for a leak is to use a little "gizmo" that you can make yourself. All you need are some fittings, a gauge, a ball valve, old washing machine hose, and an air compressor.

    You will need (1) 1/4-in tee (T), (2) 1/4-in nipples 4-inches long, (1) 1/4-in ball valve, (1) quick-connect for air compressor hose, and (1) gauge (0-100psi works best!). Find an old washing machine hose, cut it 6-inches from the connector, and place a new washer inside the hose connection. Assemble the nipples into the T on the run and put the gauge on the bull. Put the ball valve on one of the nipples and put the air hose quick-connect on the opposite side of the ball valve. Insert the opposite nipple into the washing machine hose. Use a hose-clamp to tighten down.

    Drain the water heater COMPLETELY (RE: Don't forget to TURN OFF THE GAS VALVE!). Close the hose bib at the bottom when done. Hook up your new "gizmo" to the sink and attach your air compressor to the quick-connect. Pump up the line to 100-lbs and let it sit for one hour. If the pressure drops, then you have a leak.

    DON'T DISCARD THIS GIZMO WHEN YOU ARE DONE.....You can check any type of piping by simply adding a bibcock/hose connection to the piping and put your gizmo on the end. It is better to test with air then with natural/propane gas or water.

    If you do have a leak, and it is the hot water side, run the hot water at an extremely slow pace into the sink for one hour (to cause the slab to heat up) then mop any floor you suspect the line runs under. The spot that dries first usually will be where the leak is. Since it is most likely a 1/2-inch line this process may take awhile. Best of luck! Jimmy


    • #3
      Thanks for the advice! I will try a slight variation by using a washing machine Y , gauge with female hose connection, and male hose connection blow out plug. I already have all of this or I would make it up as you described. The remaining female hose connection will go on the water heater drain. This heater is electric so I will turn off the circuit breaker.

      I was beginning to think that this side of the forum was very quiet. I spend my time mostly on the sawdust side. Thanks again, I spent three years in Lakehurst which helped teach this old southern boy that there are great people in all states.