Shutoff valve prohibition at water heater

[inspector57]

This came up at a recent SOP class. Does anyone have reference for a code or manufacturer's prohibition of a shutoff valve in the water heater hot water discharge line? I am not talking about the TPR line or water lines that have any integral Temperature or Pressure relief valves, just the standard hot water line as it leaves the tank going to the water distribution system. I have never heard of such a prohibition, but if there is one, I would like to learn.

[Jim Katen]

Originally posted by inspector57

This came up at a recent SOP class. Does anyone have reference for a code or manufacturer's prohibition of a shutoff valve in the water heater hot water discharge line? I am not talking about the TPR line or water lines that have any integral Temperature or Pressure relief valves, just the standard hot water line as it leaves the tank going to the water distribution system. I have never heard of such a prohibition, but if there is one, I would like to learn.

The only place I've ever heard of that prohibition is in home inspector education classes. It's right up there with, "you can't put splices in electrical panels" and "old plaster is full of arsenic."

- Jim Katen, Oregon

[inspector57]

That is what I have been finding. One reference given to me is: 2006 Nat Sd plumbing code 10.16.2 note 2 ..." A shutoff valve in the hot water supply is permitted." from Richard on another board.

[hausdok]

Hi,

Yeah, I agree with Jim; there are a lot of things that the manufactures warn you about when it comes to safely installing their water heaters. Rheem/Ruud has a very nice paper that explains thermal expansion in simple terms. One would expect any discussion of thermal expansion to cover a prohibition against an outlet side shutoff valve, no? Also, if such a prohibition existed, one would expect it to be in the installation manuals for these devices. I've never seen it - has anyone here seen it?

ONE TEAM - ONE FIGHT!!!

Mike

[Richard Moore]

I don't know what "safety" purpose such a prohibition would serve, unless you also can't have any faucets on the hot side that are actually capable of being shut off....which, of course, is nuts.

It makes sense that, if I have one isolation valve, then I want it on the inlet side so that I still have cold water to the home if the water heater needs changing. I just can't see the harm, or at least any more harm, in having a second on the outlet side.

[inspector57]

The theory espoused by those in the class cited the science behind the rapid expansion and flashing to steam of high pressure high temperature water in an isolated water tank when the valve was opened due to the rapid exit of water into the water distribution lines.

[Jim Katen]

Originally posted by inspector57

The theory espoused by those in the class cited the science behind the rapid expansion and flashing to steam of high pressure high temperature water in an isolated water tank when the valve was opened due to the rapid exit of water into the water distribution lines.

And why would a shut off valve on the hot water side make any difference?

- Jim Katen, Oregon

[hausdok]

Originally posted by inspector57

The theory espoused by those in the class cited the science behind the rapid expansion and flashing to steam of high pressure high temperature water in an isolated water tank when the valve was opened due to the rapid exit of water into the water distribution lines.

Jim, with respect; if that was a continuing education class and that's what the teacher is putting out there, you need to have TREC remove him from the list of those allowed to teach CEU's in your state. That's the dumbest thing I've heard since the news came out about O.J. walking into a hotel room to take back his property accompanied by a couple of guys carrying guns.

As Rich pointed out, there are already shutoff valves on that side at faucets and at angle stops. Besides, water can't flash to steam and expand like that unless it's already at boiling temps - if water gets to that temperature a shutoff valve on the hot water side is the least of anyone's worries.

ONE TEAM - ONE FIGHT!!!

Mike

[inspector57]

I agree Mike, this was not a class teaching about this per se (sp?) but an overview of the new Texas standards of practice and the valve was mentioned in passing (not in the standards) but it made my ears perk up since I had never heard of such. I questioned and was given the abbreviated "science behind the rule" rather than a code reference. Thus, I am here asking for more information.

All of use have a few crazy ideas or inspector lore, it just takes someone willing to show their ignorance (me) to ask the "why" questions to shoot them down.

[MTL_Inspet_Man]

Interesting Topic

Spent the better part of the evening scouring the installation manuals of the various manufacturers. Their manual clearly states that the water heaters should be installed per the ntational code and they all show shutr off valves on the inlet and outlet side as well as recommending a union fitting on each side to ease replacement. Something that I have never come across in my neck of the woods! The ususal way is the plumbers just cut thru the pipes and rejoin them.

My question is..... They recommend 18'' of mettalic piping in the inles and outlet side. Now I am seein PEX directly hooked to electric hot water heaters... what gives? and do the 18'' of mettalic off the tank need to be straight up and down?

Any help is appreciated...........

[hausdok]

Hi,

Pex can go all the way to the nipple on an electric water heater; it's only on the conventional gas water heater where the draft diverter is next to the nipples where you need the 18" of metallic pipe before transitioning to the PEX.

ONE TEAM - ONE FIGHT!!!

Mike

[steve morris]

Check out the spec. on CPVC(flow guard gold to be exact) they require 18" clearence also(gas water heaters) and about a million other items that are on their list(not 18" just no contact). Go to one of their CEU classes sometimes. You can contact you local FAPGMI chapter if your in florida.

[Jim Katen]

Originally posted by hausdok

Hi,

Pex can go all the way to the nipple on an electric water heater; it's only on the conventional gas water heater where the draft diverter is next to the nipples where you need the 18" of metallic pipe before transitioning to the PEX.

ONE TEAM - ONE FIGHT!!!

Mike

I thought that you guys were on the UPC up there? If so, it prohibits PEX within the first 18" of a water heater's inlet and outlet connections -- on a gas or an electric water heater.

- Jim Katen, Oregon

[hausdok]

Hi Jim,

You're right, for here; but he's not here. Code aside, manufacturers of PEX don't have a problem with hooking directly to electric water heaters - only the gas ones.

ONE TEAM - ONE FIGHT!!!

Mike