Mystery Overflow Drain

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EricJK

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I have 3 copper overflow drains on the outside of my house. One is for the hot water heater overflow, one is for the radiant heat system overflow (in-floor heat) and the last one is... I have not idea - and it's leaking. We have an outside swamp cooler and a water softener and no other appliances that I can think would need a drain. In the attached photo you can see the three drains, and the middle one is the one leaking. It stops leaking when we go on vacation and starts again when we are home. There seems to be a correlation with general in-house water use (showers, dishes, washing machine). Total amount is maybe 1/2 gallon a day. Any idea what this drain is plumbed in to?
 

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jeffmattero76

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Just guessing, but do you have a gas furnace? Mine produces condensation, which is collected in a small condensate pump, which is then pumped out. Mine goes into my laundry tub, but is it possible that yours goes directly outside?
 

EricJK

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Just guessing, but do you have a gas furnace? Mine produces condensation, which is collected in a small condensate pump, which is then pumped out. Mine goes into my laundry tub, but is it possible that yours goes directly outside?
Thanks. We don't have forced air heat, just radian pipes in the floor. The furnace for those pipes has a overflow valve - which is the drain on the left (we tested it). Also - the problem started in the summer when the heat was off.
 

EricJK

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they look like condensate drains...possibly ac or high effiency heat /hot water
I agree but our AC is an outside, ground level swamp cooler on the other side of the house (and it's currently winterized). The hot water heater overflow drain is the one on the right. Could it be tied into main home plumbing for some reason? Thanks for the help!
 

Diehard

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Okay, so you have an outside swamp cooler. So no duct work in the house.

You mentioned, one of those drain pipes is for the water heater. Just out of curiosity, is it directly from the T&P relief valve on the tank? Or is it from a drain pan under the tank. Or an open ended drain provided to catch the water from the T&P relief valve?

Are these 3 lines in/under the slab.
Have you positively identified every visible line that is penetrating into the slab? In other words are there any lines going into the slab, particularly of that same size copper line, that you may be assuming is something besides a drain?

Do you have separate hot water heaters or combination unit for domestic water and your radiant heat system?
Do you have a backflow preventer on your radiant heating system? What type?
 
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EricJK

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Okay, so you have an outside swamp cooler. So no duct work in the house.

You mentioned, one of those drain pipes is for the water heater. Just out of curiosity, is it directly from the T&P relief valve on the tank? Or is it from a drain pan under the tank. Or an open ended drain provided to catch the water from the T&P relief valve?

Are these 3 lines in/under the slab.
Have you positively identified every visible line that is penetrating into the slab? In other words are there any lines going into the slab, particularly of that same size copper line, that you may be assuming is something besides a drain?

Do you have separate hot water heaters or combination unit for domestic water and your radiant heat system?
Do you have a backflow preventer on your radiant heating system? What type?
I believe the TNPs on both the water heater and separate radiant floor heater feed their own external drains (the outside drains in the original post pictures). None of the drain lines are in the slab. I've added a few pictures to try and give you a better look. Thanks! - Eric
 

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Diehard

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None of the drain lines are in the slab.?
So what do you see on the inside face of that wall that the 3 lines penetrate?

Does that water heater pan drain go anywhere?

Do you have a make-up water connection with a backflow preventer on your radiant heat system?
 

wood4d

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in one of those photos you can see the backflow preventer to the boiler and the bottom of it is an atmospheric vent. It doesnt go straight down. Does it go outside?
 

frodo

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right here right now, over there later on.
loosen the nut on the T&P flex connector and see if it is leaking
do this when you notice the water coming out of the pipe

The picture of the 3 pipes exiting the house, is the water heater and boiler on the other side of that wall?
 
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EricJK

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Thanks everyone. I'll crawl back in there and check in the next few days. The pipes you are seeing (from my inside photos) are in fact on the other side of the wall from the 3 copper outside drains. More to come. Again - thanks for all the great thought on this.
 

EricJK

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None of the drain lines are in the slab.?
So what do you see on the inside face of that wall that the 3 lines penetrate?

Does that water heater pan drain go anywhere?

Do you have a make-up water connection with a backflow preventer on your radiant heat system?
The water heater drain pan has an outlet to the inside floor of the garage...
I'll get back you to on your other questions in the next few days. Thanks!
 

EricJK

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OK everyone - I think this attachment answers most of the questions you've asked, and I think it answers my question. The input (cold) water coming from the wall goes to both the hot water heater as well as the radiant floor heater. It also has a branch going to the wall right on the other side (inside) of the mystery drain. The branch point looked like a copper connector, but on closer inspection it may be a valve that prevents backflow to the source and routes it to the drain. Does that sounds right?
 

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Diehard

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Yes that's called a "Dual Check Valve with Intermediate Atmospheric Vent". When pressure is higher on the boiler side than on the water feed side, it dumps some water, rather than going back into the potable water feed.
It may only be the result of lower pressure on the feed side due to high use but you could check to see if the pressure climbs above the typical 15 to 20 psi(assuming that's your typical-?). If it climbs high, it could be the result of a water logged expansion tank. But if that was the case it would like be releasing more water.
They do sell repair kits if it's just a matter of a weakening unit. I'd probably live with it, once I checked out the possible causes.
 
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