Need help diagnosing a very small flow of water out the sewer pipe.

We don't know when this started but they noticed it the last time we did a septic clean out. There a very slow but steady stream of water coming from the house and if we open the cover on the pipe that runs to the septic system we can see it there.

No sinks are leaking and we put food coloring in the tanks of all the toilets but after 2 hours there's still none in the bowls. Verified that there are no leaks going down the drain in the boiler room, no showers or baths are leaking either.

Any thoughts of what else it could be?

Thanks in advance.

Washing machine taps?

No AC and no sumps, I'll check out the washing machine more closely.

Ground water? How high is the water table where you are at?

You should be able to run a snake with a camera on it up the pipe and get some kind of idea where it is originating.

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Originally Posted by def90

Ground water? How high is the water table where you are at?

You should be able to run a snake with a camera on it up the pipe and get some kind of idea where it is originating.

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Groundwater is at 350' here so that's not it, no rain recently either. I think we may have to go the snake route but we're going to need a long one. :)

Does your boiler have a condensate drain?

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Originally Posted by DFBrews

Does your boiler have a condensate drain?

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Not that I'm aware of but I don't know crap about boilers. There is one main drain in the middle of the floor so my guess is if there was a drain it would feed into the central drain in the floor. Looking around it I don't see a secondary drain and everything down there is dry.

I've ordered some green water leak tracer, I'm going to re-test the toilets as soon as I get it to be 100% sure. It is a very slow leak, like just a small trickle into the septic.

Hot water heater T&P maybe? We had this once. Changed out the T&P. Still did it. Changed out the water pressure regulator and fixed it. T&P is the "temperature and pressure" valve.

Just to be sure, look at where the fill hose joins the overflow tube in the toilet tank. This could leak without getting dye in your bowl from your tank/flapper assembly.

https://youtu.be/UygnbjIg8CY

Do you have a basement sump pump?

You might consider shutting off your water (or well) to confirm the water is coming from your water supply and not an unknown ground water source.