# water heater pan



## younger-plumber (Sep 12, 2008)

if a t&p valve blows off at full bore inside of a 24" pan will the pan be able to handle the full maximum load of the water or will some of the water inevitably overflow the pan? 20 or 22 inch round heater. I have a customer that has a pan under the heater and the t&p popped off but the floor is still soaked and they don't understand why the pan didn't catch all the water.


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## Coolcanuck (Jan 30, 2012)

younger-plumber said:


> if a t&p valve blows off at full bore inside of a 24" pan will the pan be able to handle the full maximum load of the water or will some of the water inevitably overflow the pan? 20 or 22 inch round heater. I have a customer that has a pan under the heater and the t&p popped off but the floor is still soaked and they don't understand why the pan didn't catch all the water.


Shower drain theory. 3/4" blow off under pressure and what size was the drain? I always see these pans with a 1" fitting on it and some people bush them down to 3/4". I liked the old way of doing it, blank pan and fit a 1 1/2" tailpiece. I wouldn't provide an answer of a problem with install, opens it up to insurance problems for someone, suggest a solution to try or next time it happens  and there's gonna be splashing of course


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## plumbdrum (Nov 30, 2013)

In Ma the relief can't dump in pan, 1" drain out of pan to a 1 1/4" x1" tee, relief dumps into 11/4" riser out of tee drained to floor drain or mop sink

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## Pacificpipes (Oct 1, 2013)

My pan drains are separate from t&p. They gat terminated outside


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## plumbdrum (Nov 30, 2013)

Also I think you should probably fix the reason T&P blew off first. The other allowable method my state allows if no drain is feasible is to block off drain on pan and use automatic water shutoff with water sensor .

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## Tommy plumber (Feb 19, 2010)

plumbdrum said:


> In Ma the relief can't dump in pan, 1" drain out of pan to a 1 1/4" x1" tee, relief dumps into 11/4" riser out of tee drained to floor drain or mop sink
> 
> Sent from my iPhone using PlumbingZone












FL codes need to catch up to MA code. 

We can terminate the T&P line in the pan and the pan drain by code can be 3/4".


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## Shoot'N'Plumber (Apr 27, 2013)

I don't think the gravity drained pan will keep up with a forced fed T&P, especially looking from the view point of what the capacity of the pan is after the w/h footprind takes up most of the space. Pans should only be used to prevent damage from leakage at the tank itself or supplies. The T&P needs to terminate outside or under the house or into a floor driain.


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## gear junkie (Jun 20, 2008)

Pacificpipes said:


> My pan drains are separate from t&p. They gat terminated outside


Exact same here. This one was no easy way to terminate the pan outside as the ground outside was higher. So I just ran it so a 5 gal bucket can be placed underneath.


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## MACPLUMB777 (Jun 18, 2008)

The T&P needs to terminate outside or under the house,

NEVER EVER UNDER HOUSE !

It will just hide more serious problems, like t & p running from thermal expansion, or because of a overheat thermostat on a electric water heater,

had a call once from h/o not getting hot water from heater even though burner running full force just because the t & p ended under the floor,

Per UPC code reason the t&p terminates at least 6" above ground outside house foundation were It can be seen and taken notice of !


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## Shoot'N'Plumber (Apr 27, 2013)

I agree about being able to see the leaking T&P however, here we can terminate under be house. When the heaters in the middle of the house in a hallway it's better than flooding the house


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## pianoplumber (Apr 19, 2014)

The overflow pan is a housekeeping device only. It is not a proper receptacle for a relief valve. Remember, the relief valve is a direct connection to potable water. That means wherever it terminates, you should have a proper air gap. (Open end of the pipe should not be below flood level of pan). In northern states we cant terminate outside the building due to freezing. The issue you need to address is why the t&p valve popped. In a home, my first two guesses would be: lawn irrigation backflow preventer, or the fast-acting valve of a water dispenser on a fridge.


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## MACPLUMB777 (Jun 18, 2008)

Shoot'N'Plumber said:


> I agree about being able to see the leaking T&P however, here we can terminate under be house. When the heaters in the middle of the house in a hallway it's better than flooding the house


You had better go back and check your code books !
In over 20 years of plumbing and doing water heater service work in So.Calif.
It was never in any of the code books that I worked from,
It is called piping which is part of Plumbing you run the drain out though the crawl space easy peasey, unless you are a Lazy plumber that thinks that there is a way to cheat the code because you are afraid to charge to do the job correctly,

Also check with the Uniform Building Code about dumping water under floors,

I suppose that you have never heard of things like dry rot, mold, mildew, etc,
which one do you thing the Home Owner wants ?


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## pianoplumber (Apr 19, 2014)

Again, the T&P valve is a direct connection to potable water. You should treat it like a faucet, or a hose bib, or any other kind of potable water outlet. Also, it is a safety device for a pressure vessel. Differences in state codes aside, look at the water heater mfg'ers instructions. Do they say run the line to within 6" above the floor? Or do they say send it outside, or under the house? What about testing it every so often? What does your mechanical code say about a blow-off from a boiler? If a T&P valve is set at 210 degrees, does it fall under these rules also?


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## Plumbworker (Oct 23, 2008)

water heater pan is only to catch a leak from the tank not a t&p dumping full bore.. Uniform Plumbing code states no T&P discharging into safety pan only allowed to be piped to approved drain or location outside only..


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## Gruvplumbing (Dec 26, 2013)

JERRYMAC said:


> You had better go back and check your code books ! In over 20 years of plumbing and doing water heater service work in So.Calif. It was never in any of the code books that I worked from, It is called piping which is part of Plumbing you run the drain out though the crawl space easy peasey, unless you are a Lazy plumber that thinks that there is a way to cheat the code because you are afraid to charge to do the job correctly, Also check with the Uniform Building Code about dumping water under floors, I suppose that you have never heard of things like dry rot, mold, mildew, etc, which one do you thing the Home Owner wants ?


I agree with you but why do they allow trailer manufactures to just let it go under the trailer? Or don't trailers fallow the same codes? I've always wondered that.


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## Shoot'N'Plumber (Apr 27, 2013)

JERRYMAC said:


> You had better go back and check your code books !
> In over 20 years of plumbing and doing water heater service work in So.Calif.
> It was never in any of the code books that I worked from,
> It is called piping which is part of Plumbing you run the drain out though the crawl space easy peasey, unless you are a Lazy plumber that thinks that there is a way to cheat the code because you are afraid to charge to do the job correctly,
> ...


None of the above reasons to which why I've terminated a T&P drain under the house. Inspectors in my area have always allowed the termination under the sub floor. Not once, not ever, have I been told in the handful of of times I needed to terminate under the house. Now I do digress Jerry, the times I did terminate it was at the request of the bosses when I was a lowly whipping boy employee. But rest assured, now that I'm putting my name on my work for my company, I will go the extra mile to run it to an exposed, exterior location. Afterall, if it requires more work it requires a little more cash. :thumb sup. besides, Im not actually promoting that running a T&P under the house is a good idea, nor code approved, only that I have had inspectors sign off on this, I apologize if I came off handihackish, not the intent. In fact I just added a T&P drain line to a hallway installed closet that the sears authorized installer completely left out. when I explained the concerns you mentioned, I stressed possible termite development from potential water discharge/puddling. The customer understood and I ran piping accross underside of house and terminated through exterior block.


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## MACPLUMB777 (Jun 18, 2008)

Gruvplumbing said:


> I agree with you but why do they allow trailer manufactures to just let it go under the trailer? Or don't trailers fallow the same codes? I've always wondered that.


Where I have worked on the left Coast Mobile Homes always come under different codes. Calif. Under the DMV. In Washington State under the Dept. Of Labor


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## SchmitzPlumbing (May 5, 2014)

JERRYMAC said:


> Where I have worked on the left Coast Mobile Homes always come under different codes. Calif. Under the DMV. In Washington State under the Dept. Of Labor


or in the circus code book under gypsie wagon:laughing:


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## Russell RA Tech (Nov 27, 2014)

Plumbworker said:


> water heater pan is only to catch a leak from the tank not a t&p dumping full bore.. Uniform Plumbing code states no T&P discharging into safety pan only allowed to be piped to approved drain or location outside only..


 I'm reading this thread with much interest and can see that the types of buildings you have in the States seem to be of raised construction with a crawl space underneath.

In the UK 90% of all domestic houses are laid on solid foundations, either strip or slab, but in either case there ground floor is at ground level!

Onto my point, If the T&P valve has to have an air break and it can't be taken outside and HAS to be connected to an "approved" drain, what do you do if there are no open grated drains locally?

And if the connection is made direct to a waste pipe, say an 1 1/2" waste coming from a sink what do you do to prevent the smell coming from the waste pipe?

My confusion may be because your buildings are and have always been built with this problem in mind and always have a local (what we call in the UK) trapped open grated gulley.

Hope you can clear up my confusion here

Maybe its the terminology that getting me all confused

Cheers

Russ


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## plbgbiz (Aug 27, 2010)

Most new homes here are on a slab also. We are required to provide a drain for the water heater at the time of construction.

The homes that do not have them were built before this requirement was enforced.


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## Keysplumber (Dec 28, 2011)

T&P line should always be separate from the pan drain andterminated visibly outside 6 inches above finish grade if I am quoting the code correctly


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## Will (Jun 6, 2010)

Here running the t&p outdoors is frowned upon because of the risk of it freezing. We run them to the pans here


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## Russell RA Tech (Nov 27, 2014)

Can you use an air break to drain (tundish) and then some kind of mechanical non return valve to stop the odours coming back up if you connect direct to a waste or soil pipe?


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## Dpeckplb (Sep 20, 2013)

That's interesting how you guys can run the t&p out side or in a crawl space. We have to terminate them min, 6 in Max 12" off the floor. In new construction I always put a 3" floor drain right infront of the water heater in case.


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## 89plumbum (May 14, 2011)

Russell RA Tech said:


> Can you use an air break to drain (tundish) and then some kind of mechanical non return valve to stop the odours coming back up if you connect direct to a waste or soil pipe?


We do this all the time in high-rises. 

WH in ceilings for break sinks. Drop T&P in pan with airgap. Then we install a basic metal washer box under sink in wall with its own p-trap. There's just enough room to put a 2x3 reducer in box, then drop 1" pan drain into it with an airbreak.

We install a 2" trap gaurd in 2x3 reducer to prevent sewer gas.

(not sure what tundish is)


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## JPPlumber (Jul 30, 2014)

*Tundish, terms and practices*



89plumbum said:


> We do this all the time in high-rises.
> 
> WH in ceilings for break sinks. Drop T&P in pan with airgap. Then we install a basic metal washer box under sink in wall with its own p-trap. There's just enough room to put a 2x3 reducer in box, then drop 1" pan drain into it with an airbreak.
> 
> ...


As plbgbiz kindly posted an illustration in another thread which I am too computer challenged to find...a tundish is an airgap similar to what we would use on an RPZ drain valve.

I also appreciate the info above about the trap guards, haven't seen them yet in residential applications, but all I do for the most part is residential service. Saw them for the first time at my church and thought they were some kind of "knock out" that never got removed.

The more I learn I find the less I know and how so much of what we do is affected by our regional practices or requirements or experience..and here in Dallas/Fort Worth suburbs it can vary city to city or inspector to inspector. 

In Fort Worth, T&P 3/4" with fall to outside between 6" to 24" ...if possible, because some older homes on slab have existing 1/2" discharge with the water heater in a hall closet on the interior of the house. Solution in one suburb....pipe to 5 gal. home depot bucket with lid and drill hole in lid. Water alarm in closet. Basements or floor drains are almost non existent here. Crawl spaces are far more common in older homes...if there is even room to crawl.
Solution in suburb...drill hole in floor and dump under house into crawl space due to the fact so many homeowners complaining to the city about plumbers "overcharging" about bringing existing homes up to code.


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