I recently had some electrical work done at my house, and as part of that, the power was shut off. After a few minutes, we noticed water coming from the closet containing the hot water heater and furnace. There was a slow and steady trickle of water coming out of the condensate pump, and we could feel the heat in the discharge line connecting the pump to the t&p valve.

The next day, I talked to two different plumbers about this. One said that line should be going to a drain, but there's no drain in my basement. The other said it was ok for that line to be connected to the pump, but there should be a shut-off valve on the hot water side of the heater.

Who (if any) is right? I'm most interested in what would be considered up to code in Pennsylvania. Since that's a vague question, I'll also ask a specific one: what's the best thing for me to do to ensure the next time I lose power, my basement doesn't slowly flood?

Edit: because a picture is worth a thousand words.

water heater and furnace

  • 1
    What make and model is your condensate pump? I somehow doubt it's rated for what a T&P valve will discharge when it's busy preventing your water heater from putting a hole in your roof.... Aug 12, 2018 at 2:32
  • 1
    @ThreePhaseEel: it's this one; there's a spec sheet on that page too (though I don't know what I'm looking for).
    – Steve D
    Aug 12, 2018 at 2:39
  • I need to ruminate on this for a while -- you're in a real sticky wicket, since I suspect your pump is representative in topping out at 120degF inlet water, and could be damaged by the 180+degF water coming out of a T&P that's doing its job... Aug 12, 2018 at 2:41
  • i9n normal; usage the flow from that valve will be very slow an should cool sufficiently before it reaches the pump, if the thermostat fails there's going to be a mess no matter what you do.
    – Jasen
    Aug 12, 2018 at 3:34
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    I don't like the idea of just slapping in a tankless, as a unit replacment for a tanked heater; that just leads to a more quirky heater. A tankless deserves the benefit of more careful system design, so it lives up to its impressive potential (not least, being able to be installled in many more choices of location). So I would start thinking hard about that... real fast... Meanwhile see if just swapping the T&P will get you by... Aug 13, 2018 at 2:19

1 Answer 1


If the T&P relief valve opens for most reason it is designed for, (over pressure or over temperature) the water flow can be a slow trickle or could be a fast and sometimes violent event. If it is a slow trickle, the pump will handle the water but if it a quick discharge there is going to be a lot of water flow. As far as the valve on the hot water side of the heater, I have no idea how that will alleviate any of your problems, unless i do not understand it's function. Without a drain in the basement, I would not store anything in that area that could be harmed by water. If the water heater's T&P valve is flowing a small amount of water you need to find out why this is happening. If it leaks all the time you may need a PRV to limit the water pressure in the house or the T&P valve may be worn out and need to be replaced, and if happens only when you use hot water and the water is being reheated , you may need to have an expansion tank installed to accept the expanded water as it is being reheated.

  • Thanks for the answer! What do you think the best option here is?
    – Steve D
    Aug 12, 2018 at 14:52
  • Carefully re-read my answer and determine when the water is flowing from the T&P valve. That will determine what your need is. However, if you do not have an expansion tank on your hot water tank, that is the first item I would add, it is a code requirement where I live. You could buy a pressure gauge that screws onto a faucet with threads to check the standing water house pressure. My pressure is usually around 75 PSIG. And If the existing T&P valve is 10 years or older I would replace it.
    – d.george
    Aug 12, 2018 at 16:23
  • Thanks again. I had a plumber already install the shut-off valve and a new T&P valve. I'm going to have an HVAC specialist come out and talk me through adding an expansion tank and battery backup for pump.
    – Steve D
    Aug 13, 2018 at 3:52

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