Two Attic Water Heaters (GAS)

Ken Larson · 09-19-2007, 02:25 PM

Does anyone know the code reference for double attic water heater installations. I wrote up a new home that added another water heater in the attic (after the fact) when the buyer discovered only one was installed and he paid for two.

Well, the plumber decided to just tap into the same drain line and the same TPRV line as the original water heater. Plus he used PEX for the TPRV drain and not a pressure rated relief line.

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**Scott Patterson** · 09-19-2007, 02:35 PM

The codes do not address multiple water heaters as far as I know. The installation requirements will be the same if only one was present. Each must have their own TPR line and it can not terminate in a "T" like it is doing in the picture. They both need to terminate in a visible location. This would fall under the TPR valve (Watts most likely) manufacturers installation requirements.

As for the "Smitty Pan" or the emergency overflow pan, I don't know of any reason they can't join together as in your picture.

**Jim Luttrall** · 09-19-2007, 03:01 PM

IRC 2003 P2803.6.1 Requirements of discharge pipe.
..."The discharge from the relief valve shall be piped full size separately to the floor, to the outside of the building, or to an indirect waste receptor located inside the building...."

The discharge from a relief valve shall not be trapped. The diameter of the discharge pipe shall not be less than the diameter of the relief valve outlet.
...so as to drain by gravity flow...
I thought it was supposed to be rigid pipe, but I can't find a requirement in the IRC other than the "no trapping" provision. I see very little PEX that is 3/4 inch, are you sure they used full size of the TPR valve with no reduction?

Drains shall comply with 2904.5. Hot water distribution pipe and tubing shall have a minimum pressure rating of 100psi at 180F

Drain line for pans is required to be 3/4 inch minimum or the outlet of the relief valve which ever is larger. I think a case could be made that the drain line would have to be up sized to accommodate two times the minimum, but that is just my opinion.

**Billy Stephens** · 09-19-2007, 03:46 PM

Originally Posted by Clay E White

Is there a proper walk/work platform to/for the waterheaters?

Clay,

Min. 30" Working Space in front 06IRC(1305.1)

Not sure what you mean by proper walk/work platform to.

Light Bulb!
Sorry Clay, 24" clear walkway !!! Duh!

**BARRY ADAIR** · 09-19-2007, 04:49 PM

That pipe insulation shall not be within 6" of the draft hoods or flues ...

Ken Larson · 09-19-2007, 04:49 PM

The walkway or other issues have already been taken into account. I was just thrown when I saw how this plumber attached this second water heater. I've seen quite a few double water heater installations, it's getting more common with the the 2500 + sq ft homes, but not like this.

Just down the block I inspected another new home by a different builder and his was picture perfect, side by side water heaters and both on separate drains and separate TPRV lines, each installed as if they were individual units as I feel they should be.

I checked my IRC books and couldn't locate any double water heater references for attic installation so thanks for pointing out what little there is.

**Jerry Peck** · 09-19-2007, 04:53 PM

Being as two water heaters were paid for, and intended, it is probably safe to assume (but needs mentioning here just in case) that the trusses were designed for the weight of the second water heater?

Empty tank = 80 pounds? (guessing)

50 gallons of water = 430 pounds (approximately)

Tank full of water and related piping = 525 pounds? (guessing)

Ken Larson · 09-19-2007, 05:23 PM

Correct as usual Jerry, I mentioned that in my report also.

But....focus, focus....My question was about the TPRV and drain lines. Everyone always tries to throw in info that didn't pertain to the original question. I love all the help, why is there the assumption something else was missed?

Thanks for watching my back though, I think I got all the other stuff. Or, at least I hope I did. LOL

**Jerry McCarthy** · 09-19-2007, 06:21 PM

The TPRV on those WHs is a wrong as wrong can be. It would be interesting to know if a permit was pulled for that and the local AHJ looked at it?
If so perhaps the inspector's seeing eye dog couldn't make it into the attic?

**Jerry Peck** · 09-19-2007, 06:56 PM

Originally Posted by Ken Larson

But....focus, focus....My question was about the TPRV and drain lines.

I know, but that had already been answered.

why is there the assumption something else was missed?

There is no assumption of that, just "making sure", like you said, we are just ...

watching my back though,

**BARRY ADAIR** · 09-21-2007, 05:20 AM

Originally Posted by Jim Luttrall

I thought it was supposed to be rigid pipe, but I can't find a requirement in the IRC

Once PEX is "properly" installed and secured to the structure would it not then be a "rigid" installation?

**Jerry Peck** · 09-21-2007, 06:07 AM

Originally Posted by BARRY ADAIR

Once PEX is "properly" installed and secured to the structure would it not then be a "rigid" installation?

No. The pipe is still 'flexible pipe'.

However, there is no requirement for it to be "rigid".

From the IRC.

- P2803.6.1 Requirements for discharge pipe.

The discharge piping serving a pressure-relief valve, temperature relief valve or combination valve shall:
- - 13. Be constructed of those materials listed in Section
P2904.5 or materials tested, rated and approved for
such use in accordance with ASME A112.4.1.

In Table P2904.5, you will even find poly bute listed (yep, it's still approved by code), so now you will need to go to each type of pipe and find out if it is approved or not (some are and some are not), such as PB is not, I believe PEX is not (but it might be). I don't have the ASME standards, but whatever is approved for this use would be listed in ASME A112.4.1. Copper is, galvanized is, CPVC is. Probably any type of metal pipe is.

There are 13 types listed in Table P2904.5, 6 are metal of some type, CPVC is there, PB is there, that leaves 5 which would need to be checked on, and if PEX is not, that leaves 4 which need to be checked on. Of that 4, 2 are derivatives of PEX, leaving 2 unknowns (both some type of polyethylene or polypropylene). I suspect those last 2 are not either.