1/4 cpvc pipe

Need help trying to find out why water is comming out of a 1/2 inch pipe at the rear of a house ever 2-4 min. It is not the tpr discharge pipe or condensate line and the water heater has an expansion tank. The pipe is located about 1 foot from the rear hose faucet. The water pressure for the house is 80 psi +/- 2 psi. When I shut the water off to the water heater the flow out of the pipe came just about to a stop; but then it was making a banging noise. Another inspector told he thought it was a expansion valve; then I told him about the expansion tank.
Not sure if this will help any but in the front yard near the water meter was a green pvc pipe near the meter with Gate Valve marked on it.
Any help would be great, will not allow me to post a pic.

1/2 pipe

It is an 1/2 inch

Hi Phil,

Without a pic… it’s a bit tough… where exactly does the pipe terminate or come from? Does it just hang out of the wall… is there an enclosure or box or ? You get the idea.

I’m not sure where a 1/2" cpvc pipe fits into a Hot Water discharge system of any kind, but there may be some things going on behind the scenes, so to speak. Or… is there a drip pan for water heater (1/2" would be wrong size)… or a condensate pump for XXXX?

Is it an older house that maybe has a pressure relief (original equip) valve behind something, ie. an enclosure?

You mentioned when you shut the system off, you here a banging noise… does it sound like water hammer? Also, you mentioned that the flow from the pipe seems to “just about stop”… it would be good to know if it does in fact stop it or not.

Water hammer coming about when the supply is cut off would indicate not only some type of trouble (can’t guess as you didn’t indicate where/what part of home) may be present as well as water continuing to flow? I would assume a “trickle” effect is present to create the hammer, but as I don’t know what’s going on, we’d want to make sure a cross connection isn’t present too.

You mentioned a meter, did you check it and see if water is flowing/running somewhere, as indicated by the creep meter (small triangle)?

Ultimately, a plumber may be needed to look at this, if it’s your home… call one (a plumber). If it’s a home you’ve inspected, maybe try to accurately describe what you can see and what you can’t, to help a buyer make an informed decision.

Hopefully, my poking about with a few questions may lead to a response from you or help in some way.

If you post some additional information, you may get some other responses here.

Are you sure it’s not a secondary condensate drain line?

It’s not a secondary condensate line; it’s about 1ft from the ground and about 10 inches from the rear hose faucet and both of of these are under the kitchen window. There is the interior cut-off for the rear hose faucet located under the kitchen sink, did not see the 1/2 pipe there. The water would discharge every 2-4 min and just before it did you could hear a thump sound. The house was built in 99, 2 story on a slab. No toilets running, shower,sink, tub and exterior hose faucets. No water running and still would discharge. When I shut the water off to the water heater it did not stop completely but slowed to a trickle;then it started to make the banging sound, not the same sound you here with water hammer. It was a house I inspected and did say & write that it needed futher evaluation and repairs by a plumber.

Silly question… but there isn’t a small electric water heater in/under the cabinets somewhere as a supplement to the main water heater…? Maybe with a bad TPR valve or a stuck temp control? Maybe even a poorly installed (or malfunctioning) water filter system, that is purging and connected to the hot water??? Which could have made it go KaPuT :mrgreen:

Wish I could help more… without the Thump sound and such, I would have thought a condensate pump or as Chris mentioned a secondary or something… the regularity in the timing could mean a few different things…

In retrospect, a couple of things to try problem solve… a meter check (if city/public supplied water) to see what was happening before and after water heater water supply valve is shut off, when the hot water faucet in kitchen was opened… did the intermittent flow stop?

Pressure gauge on hose bibb (you mentioned one adjacent to the mystery pipe) to watch for spike/fall in pressure.

Thanks for yalls help!