TPR Valve on Mini-Tank Water Heater

[TromboneAl]

I'm about to install the water heater shown below.

[-]I was surprised to see that it comes without the TPR valve on the top, but I can buy that.[/-] (It was stuffed into the bottom of the unit.)

My understanding is that I should either route the output from that valve down to a bucket on the floor, or through the wall and to the outside.

However, in the video below, the installer doesn't route that relief valve anywhere.

What should I do?

Install a Mini Water Heater DIY (#5251) - YouTube

 

[samclem]

What should I do?

If that valve ever "does its job" it could be spewing lots of high-pressure scalding hot water. To minimize the physical risk (when you open the cabinet doors) the water at least needs to be directed in a safe direction (using pipe and fittings that can stand hot water: hard-drawn copper, CPVC, or galvanized steel, not PVC). To reduce property damage the drain should go where the water can be gotten rid of without flooding your kitchen or destroying your cabinets.

Code requires the TPR discharge pipe on full-size water heaters to be pointed down and to terminate within 6" of the floor. I don't know about the requirements for this installation, but you'd definitely want the pipe pointed in a safe direction.

A catch-pan under the water heater should also be installed and drained somewhere safe. It's a water heater, it's eventually going to fail.

If you've got a basement with a floor drain located directly underneath your kitchen, that would be a great answer.

 

[ERD50]

The instructions I saw from Home Depot said T&P valve included, same with the ones I saw on Amazon.

+1 to what samclem posted. It's got to go to a drain. If you run it outside, you should ensure that it can't get blocked by anything.

I'll be curious to hear how this works for you, and whether a mixing valve is needed or not.

-ERD50

 

[travelover]

...........
A catch-pan under the water heater should also be installed and drained somewhere safe. It's a water heater, it's eventually going to fail.

If you've got a basement with a floor drain located directly underneath your kitchen, that would be a great answer.

I agree, a pan underneath is a good insurance policy plus the temperature overflow valve can be routed to discharge into the same pan.

 

[TromboneAl]

Thanks, Sam.

Here it is, sitting where it will be installed. It sounds like you are saying that to do it right, I need to put a hole where the red arrow points to, and have a copper pipe that connects the TPR valve to the outside.

But are you also saying that having the valve just point the discharge to the back of the cabinet, would be reasonable, at least for safety?

The tank holds 2.5 gallons -- if it blows, how much water is going to come out?

And if it fails, I'm assuming that water could flow out continuously -- in which case a catch-pan isn't going to help.

Should I have the plumber do this?

 

[NW-Bound]

I am sure that the building code would require that the discharge pipe goes through the exterior wall and discharges down to the ground. That is done in my homes, even though in one home the water heater is in the garage. In the other home, the water heater is in a closet in the middle of the home, and the discharge pipe has to go a long way under the crawl space to reach the exterior foundation wall.

 

[samclem]

Should I have the plumber do this?

You don't get a story that way!

Like travelover suggested, I'd just drain the TPR valve directly down the side of the tank, (at the back but still visible from the side) to a point a few inches above the catch pan placed under the unit. Code where I'm at allows that, there's no requirement that the TPR discharge pipe itself go outside. The catch pans have their own drain in the side, and that's what I'd take "away." That way you can see if the TPR is leaking and see if the tank is leaking. I would probably drain the unit down through the base of the cabinet and the floor.

I'd also spend $20 on a cheap water alarm and put the sensors into the drip pan, it will let you know if you've got a problem and save you lots of money.

The amount of water that can be leaked is unlimited (if the valve fails "open" or when the tank starts leaking), but because the catch pan has a drain it will get rid of it.

I don't have a great answer about where to drain the tank. No basement with floor drain, laundry sink, or shower? Going outside will build a highway for bugs and will allow cold air to continually come in. Maybe some sort of P-trap outside? Does it ever get below freezing where you are? I'm sure there's a clever answer.

 

[TromboneAl]

Yeah, I don't see any option for draining the catch pan. Sending the TPR pipe outside would be the easiest.

 

[ls99]

There is no need for the TPR output pipe to be copper, black iron would work just fine.

If you feel energetic you could plumb it into the drain pipe past the dispenser. Don't know what codes call for. There would be no odor issues since the walve only opens when overpressure is forcing it open.

 

[M Paquette]

If you feel energetic you could plumb it into the drain pipe past the dispenser. Don't know what codes call for. There would be no odor issues since the walve only opens when overpressure is forcing it open.

Code will call for an air gap in that path. The idea is to avoid any possibility of cross-connecting the clean water and drains systems in the event of a valve failure. (and just because something sounds incredibly unlikely doesn't mean it won't happen. Ask any nuke operator about the incident reports...)

The hardware for such an air gap looks like a drain pipe ending a few inches above a funnel. Not in, but above. The funnel then goes to the drain system.

 

[calmloki]

Code will call for an air gap in that path. The idea is to avoid any possibility of cross-connecting the clean water and drains systems in the event of a valve failure. (and just because something sounds incredibly unlikely doesn't mean it won't happen. Ask any nuke operator about the incident reports...)

The hardware for such an air gap looks like a drain pipe ending a few inches above a funnel. Not in, but above. The funnel then goes to the drain system.

I've never seen such a cute unique purpose bit of plumbing. Wonder how the sewer gasses stay blocked by a water dam in that unused U trap? You dump a bit of water in every couple weeks?

I'd be loathe to poke a hole out the exterior wall just for the TP drain and would expect that the floor of a cabinet gets used, whether it had a catch basin or not - that being the case I wouldn't have a catch basin. I'd just run the TP drain down to 6" above the cabinet floor and maybe add a water alarm below it (actually I wouldn't, but I'm a gambler and figure I'd notice a leak under the kitchen sink).

 

[bjorn2bwild]

The TPR valve on my outdoor mounted tankless water heater has tripped for no apparent reason several times (5-6) in the last 5 years. It did not turn off by itself - I had to burp it a few times to get it to stop. Probably an overly sensitive valve, but I would not want that to happen under the sink without a good path to the outside. I would use copper pipe.

 

[samclem]

I've never seen such a cute unique purpose bit of plumbing.

(Steady . . .)

 

[M Paquette]

I've never seen such a cute unique purpose bit of plumbing. Wonder how the sewer gasses stay blocked by a water dam in that unused U trap? You dump a bit of water in every couple weeks? I'd be loathe to poke a hole out the exterior wall just for the TP drain...

The silly pipe and funnel (and water trap that will always wind up dry) are why folks poke holes to the outside for the drain. The pipe and funner are allowed under code, but aren't the best choice IMHO. I've seen fine mesh bags fastened on the outside drain line as bug screens, but I don't know how well they work.

 

[travelover]

Plan B: a shallow pan with no drain and a water sensor alarm as samclem mentioned above.

 

[samclem]

Plan B: a shallow pan with no drain and a water sensor alarm as samclem mentioned above.

Or, Plan C: As above, but add an automatic shutoff valve to the input valve on the water heater (you've got AC power right there!). Water sensor for the valve goes in the catch pan. No matter what is causing the leaking, the water is turned off.

This way you get hot water, and a conversation piece that will amaze and astound your friends.

Would I do it? I dunno. $130 bucks sounds like a lot, but it's less trouble and hassle than drilling through the wall, and less money/hassle than replacing a ruined cabinet/cabinets. It takes care of the emergency day or night, whether you are home or not. It's a toss-up in my book.

If it DID ever prevent a flood, you'd feel brilliant!

Link: Floodstop Safe Home Products

FloodStop 3/8 Inch Valve for Water Heater/Softener, FS-3/8C-V4

 

[REWahoo]

Plan B: a shallow pan with no drain and a water sensor alarm as samclem mentioned above.

+1

That's what we have.

 

[TromboneAl]

Need some Help

OK, the TPR thing worked great:

However, my lack of plumbing skills are causing me grief.

Main problem is this cap that I bought to seal off the unused line to the dishwasher.


I think the problem is that I didn't also get a washer. It leaks. I made a washer out of some neoprene, but that didn't solve it.

Do I just need a washer, or is this the wrong thing for a compression fitting?

Also, I'm having some leaking at the base of the TPR valve. I used plumbing tape, but I think I need to do a whole nother turn to get it tight enough. I don't know if it will go around far enough.

 

[bjorn2bwild]

The cap looks like it is for a flare fitting - close but not quite perfect. That is the problem with plumbing. I prefer paste to teflon tape. If the valve is already tight, it is doubtful that you will get a full 360 without a problem.
If you need to turn the valve more to stop the leak you will need to correct with angle fittings - 22 1/2, 45, 90 degree.
The use of a union between the valve and tank will allow you to tighten as needed, but will change the height and will need to be corrected with angle fittings.

 

[TromboneAl]

I have not been using the tape right. I've put about 1.5 turns on, and from a youtube video, I've learned I should be putting at least 5.

I hate plumbing.

 

[ERD50]

Is there something to grab on the tank side when you tighten the TPR? You don't want to just twist against whatever it threads in to. You need to be able to grab that side with a wrench or pipe wrench so you don't twist it off.

1.5 turns of tape seems light. All those gaps need to be filled and compressed. I also prefer the newer 'pipe dope' that works on metal and PVC. It lubricates the threads too.

edit/add: I also think that that compression fitting must need a washer or a compression ring. But I could not find that info. But they are NOT meant to seal on the threads, so using more tape is probably not the right way to go.

I've also read that a p-trap in the drain is not allowed by code. It would trap water that could get sucked back into the clean water supply if pressure was lost, and the valve leaked... unlikely, but those codes are what help keep things safe.


-ERD50

 

[TromboneAl]

More tape fixed all the leaks.

But I plugged it in, and it doesn't work. The light doesn't come on and it doesn't heat the water. Tech support at Stiebel Eltron is overloaded, and I can't get through.

I hate plumbing because there's never any room to work, you have to contort your body all the time, and one mistake leads to a flood.

 

[calmloki]

More tape fixed all the leaks.

But I plugged it in, and it doesn't work. The light doesn't come on and it doesn't heat the water. Tech support at Stiebel Eltron is overloaded, and I can't get through.

I hate plumbing because there's never any room to work, you have to contort your body all the time, and one mistake leads to a flood.

Look for a reset button on the thermostat by the heating element. Push same in.

 

[bjorn2bwild]

Are you using the garbage disposal outlet? If so, it needs to be switched on for power.

 

[samclem]

Are you using the garbage disposal outlet? If so, it needs to be switched on for power.

If both outlets are controlled by the switch (which shouldn't be the case). If they are both controlled by the switch, it might be easy or hard to make it so that the WH outlet is always "live", depending on how the disposal is wired.
- Another option: a tripped GCFI breaker/protected outlet. But I'm guessing Al has already checked to make sure there's power to the WH outlet.

I'd bet on the reset button.

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