Water Heater TP Valve Discharge Location - basement w/ no drain

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ruffryder

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Hello all.

I am installing / relocating a new gas water heater into the small basement under my house. The basement is reached by some outside stairs that are concrete, and then through a metal door. The basement floor is concrete and does not have a drain, though there is a dry well at the landing at the base of the stairs that handles the water from the rain. I also dump the dehumidifier bucket down it when I empty it. The walls of the basement are concrete cinder block filled with cement.

I have been looking more into the requirements of the TP valve discharge and note that there must be an air gap between the TP valve plumbing and drain. I am thinking about installing an above floor drain that would dump into the outside drywell, through the hole in the concrete wall by the door. The above floor drain would essentially be a 2" pipe that has a deep water trap, allowing for the TP valve discharge tube to be placed above it, leaving an air gap. The drain would also then be used for condensate from the water heater and potentially a furnace.

The purpose of the water trap would be to ensure cold air and moisture doesn't enter the basement area. The trap would be located in the heated area of the basement, so as to mitigate any possible freezing.

Your thoughts on if this is an acceptable idea would be appreciated.
 

ruffryder

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Is my question dumb? I guess I have seen conflicting code requirements in that the TP valve discharge can be plumbed outside, but also requirements where an air gap is required if the valve is discharged outside of the room it is located in.
 

Reach4

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Is my question dumb?
No. That is a simple, if not rhetorical, question with an easy answer. The rest of it -- less so. I am not a plumber.

I think you are usually allowed to have the T+P overflow pour out onto the floor, as long as that exit is no more 6 inches (not sure of how low it can go) off the floor. At worst, your system would seem to accomplish that, even if the outside exit would freeze up.

The exit is supposed to be visible and maybe even obvious. I think you meet that too.

3/4 galvanized pipe can be used for that pipe to the exit. That is about the only long-term new use of galvanized pipe that makes sense in a house to day IMO.
 

Jadnashua

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Some places allow it to drain outside, but with the rigid requirement that the flow must not be constricted and must gravity drain the whole line. Being in a basement, you probably cannot achieve that.

That outlet is an emergency, safety outlet, and except when you test the valve, should never open on its own so most places don't worry too much about the outlet. If it is in living spaces, you'd want to deal with it, but probably not necessary in a crawlspace. It is nice to know when it opens, and there are some devices that can be used to detect it to alert you if it's not in an area you pass by often. One that intrigues me is a product called a WAGGS valve...you'd need to install the WH in a pan, and then hook up the WAGGS valve (warranty only applies if done by a certified installer), but if it detects a leak, it will shut off the incoming cold water and shut off the WH so it won't run. It's a one-time use device that does not rely on any power to function...it uses a dissolvable puck to release the spring-loaded valve and open a switch that can be used to disable the WH. Same functionality as what they use on life vests on airplanes that inflate them when they hit the water.
 

Cacher_Chick

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We have basements, many without floor drains. In normal operation, a T&P valve will never discharge any water, so there is really little reason for a drain. The chances of a T&P discharge in a properly plumbed house are about the same as the chance of any other kind of plumbing leak. If you are worried about it, put a battery operated water sensing alarm on the floor ($10) so you are alerted if there is a problem. Particularly in an unfinished basement, there is really no harm done by water unless you let the basement fill up like a swimming pool. I would much rather have a T&P discharge somewhere where someone is going to notice it right away, because it is a sign of a bigger problem.
 

Gary Swart

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Might be wise to consult your local code enforcement. Whatever method you use has to pass inspection or should code compliant even if not inspected. I'm sure this is a common question and maybe handled differently from place to place. I'm sure the pipe for the drain must be either galvanized or copper and for sure not PVC.
 

ruffryder

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I am going to call the local authority tomorrow morning for clarity. Below is the code being used.

"Discharge pipe shall discharge independently by gravity through an air gap into the drainage
system or outside of the building with the end of the pipe not exceeding 2 feet (610 mm) and
not less than 6 inches (152 mm) above the ground and pointing downwards."

In reading this, the air gap is only required when going into the drainage system and not required for being piped directly outside of the building? I guess this would make sense since the air gap is there for cases where the drainage system might be clogged or if it backs up?

I will let you know what I find out.
 

Jadnashua

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If your WH is in the basement, it may be impossible to run the drain outside without trying to defy gravity! If the discharge is not in a finished area, it is very common to just let it drain on the floor. It should only drain during a fault, never during normal operations. If it's a slow leak, a drain pan can help and will allow you to direct it's outlet somewhere less problematic, but you must retain the air gap between that outlet and the pan.
 

FullySprinklered

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Hereabouts, if you can't have a gravity drain, you would run the discharge up and out of the foundation, then elbow down to 6 inches above the dirt. At the water heater you would put a boiler drain or some such where the discharge goes from vertical to horizontal before heading up and out of the house. The T&P valve guts can't handle staying wet, it seems.
 

ruffryder

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I have a dry well at the landing for the outside basement entrance. The height between the top of the water heater and the well is approximately 5 ft (water heater is higher and only 5 - 8 ft away from outside wall), so I don't see a problem with configuring a gravity drain. The basement is concrete floor with all purpose carpet so I am fine with just letting it run to the ground too, though not ideal. Also, code here states that the discharge pipe can not go to the water heater pan, if required (only for wood floors).
 

WorthFlorida

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The air gap is to prevent any water from ever being sucked (or siphoned) back up into the water heater. All the planets would have to line up before it could happen. The code is essentially saying any potable water source cannot be tied directly to waste or drain line. The T&P will only happen when the should the temperature get to high and the pressure build to a dangerous level. For any water to discharge is rare and to save the day.
 

ruffryder

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Well, I got my answer. I can run the tp valve discharge to the dry well outside, but I will need to install a secondary pressure valve set at 125 psi from the incoming cold water line to the water heater that discharges to an approved location, in this case outside but not in dry well. Like all temperature or pressure valves, there can be no shut off between the device and the valve and the valve must gravity drain to an approved location.

Thanks for everyones thoughts and insight.
 

Reach4

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Well, I got my answer. I can run the tp valve discharge to the dry well outside, but I will need to install a secondary pressure valve set at 125 psi from the incoming cold water line to the water heater that discharges to an approved location, in this case outside but not in dry well. Like all temperature or pressure valves, there can be no shut off between the device and the valve and the valve must gravity drain to an approved location.
Any air gap required?
 

Cacher_Chick

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I cannot comprehend why anyone would allow a T&P to discharge anywhere that would not be noticed by the residents.
 

ruffryder

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Any air gap required?
So if you are discharging directly outside, the air gap is the outside termination. No other air gap required. If you are terminating in a floor drain or other system, you must have an air gap. As mentioned before, the issue is to make sure you don't contaminate the potable water supply.
 

ruffryder

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I cannot comprehend why anyone would allow a T&P to discharge anywhere that would not be noticed by the residents.

If they go to a floor drain via an air gap, will residents notice any draining? I would think not?

Maybe if it went to a laundry sink or something like that, or the floor of a garage.
 

Cacher_Chick

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I cannot comprehend why anyone would allow a T&P to discharge anywhere that would not be noticed by the residents.
 
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