Maximum distance allowed away from unit for PRV valve?

[EIR]

To make draining the PRV easier, and since tankless units have the PRV plumbed into the output side of the heater, is there a code to how far one can located it away from the physical unit?

I'd like to plumb mine out the side of the output valve and go up two or three feet to get the slope needed for a continuous downward drain to daylight.

Tanked units typically have a physical location on the tank which dictate its location.

I assume the closer the better.

 

[EIR]

nvm i think i figured this one out myself.
Since tankless units only require pressure relief valves since over temperature is controlled internally (no T&P valve required).


from watts

Where is the proper location for a pressure relief valve on a hot water storage system? For pressure relief only, you can install a plain pressure relief valve anywhere in the system simply because pressure is common to all parts of a system. However, we recommend that you install it as close as possible to the equipment which it is to protect. We recommend simple pressure relief valves only for unfired storage vessels not subject to possible overheating. Note: never install a shutoff valve between a relief valve and the tank!

 

[Sponsor]

 

[Stuff]

Lots of places still require temperature and pressure relief valves no matter what type of heater you have. PA officially goes by 2009 IRC which lists the rule.

The valves shall be installed such that the temperature-sensing ele-
ment monitors the water within the top 6 inches (152 mm) of
the tank.

 

[EIR]

With no tank then within 6" of what?

 

[Stuff]

Good question that can only be answered by your local authority. Here it is the Allegheny county health department.

Normally it would not be allowed for the discharge pipe to go up as that would be against gravity.
http://codes.iccsafe.org/app/book/c...tional Codes/IRC/Chapter 28-Water Heaters.pdf

 

[EIR]

I know. Hence why I said like like to plumb the physical prv up higher on the side of the tankless unit to allow a constant vertical drain for the prv...instead of just threading it onto the tankless valve set.

Id use the intended port on the tankless hot water disconnect valve and just bring the physical prv valve out to the side alittle and up 2-3 ft. Still no operable valve between it and the water heater. Still physically within 6" of the tankless unit itself....just has a alittle more pipe between it and the unit.

Since it's a prv valve on mine only I don't think it matters.

Good question that can only be answered by your local authority. Here it is the Allegheny county health department.

Normally it would not be allowed for the discharge pipe to go up as that would be against gravity.
http://codes.iccsafe.org/app/book/content/PDF/2009 International Codes/IRC/Chapter 28-Water Heaters.pdf

 

[EIR]

I am somewhat frustrated with the plumbing and mechanical codes. A lot of installation info so far has been "contact the ahj". As an electrician by trade I should be able to have the code book in my possession and have most of the information needed to complete the installation without having to badger the ahj...just like the NEC. Yes occasionally a town will have amendments. But have the most current NEC can have even a beginner get their way through a compliant electrical installation.

My town still uses the national standard plumbing code 2009. I've combed through the code book a few times.

Very little useful info is there pertaining water heaters.

The mechanical code referenced by my town isn't much better.

 

[Reach4]

Very little useful info is there pertaining water heaters.

A document labeled "Pennsylvania Plumbing Code"
https://archive.org/stream/gov.pa.plumbing/pa_plumbing_djvu.txt says

502.1 General. Water heaters shall be installed in accordance
with the manufacturer's installation instructions. Oil-fired
water heaters shall conform to the requirements of this code
and the International Mechanical Code. Electric water heaters
shall conform to the requirements of this code and provisions
of the ICC Electrical Code. Gas-fired water heaters shall con-
form to the requirements of the International Fuel Gas Code.​

I would assume (I know what they say) that the manufacturers would make their WHs to conform to those standards, No?

Even with other codes, isn't it the manufacturer's job to provide the T+P function?

 

[EIR]

I suppose on tanked water heaters.
My manual says this

To complete the installation of the water heater, you must install
an approved 3
/4 in, maximum 150 PSI pressure relief valve on the
hot water outlet. The water heater has a built-in high temperature
shut off switch, so install a “pressure only“ relief valve. This valve is
not supplied, but is required. The following examples are approved
for use with the water heater:
-
Wilkins P-1000A (Zurn Industries)
-
Conbraco 17-402-04
-
Watts Industries 3L(M7)
-
Cash Acme FWL-2, 3
/4 in
The pressure relief valve should be placed as close to the water
heater as possible. No other valve should be placed between the
pressure relief valve and the water heater.

That's all well a good. Just because the manufacturer states it doesn't mean it passes code.

Plenty of mini split manufacturers state to run their proprietary cable between the outdoor unit and the indoor evaporator head through the building and wall assemblies but will fail inspection because it is not rated for concealed use in wall assemblies as it's not rated as building wire.

If the plumbing codes simply state "follow the manufacturer" then I'm all for following a simple installation manual.

As close as possible as mentioned in mine is a big wide grey area to me. In electrical terms we often consider close as "25ft or within sight".

I'm not trying to argue with you. I know I could just call and play phone tag with my building office on every little detail.

I just want the inspector to show up once and pass it. I feel there is more ahj opinion and preference than code.

 

[Jadnashua]

You don't want the relief valve's outlet to ever go up...it needs to drain down. If it were to go up, it could hold water, potentially freeze, or get clogged with debris. It needs to be able to drain via gravity so that all of the water is gone, and it only gets wet during a fault.