Thread: TPR Valve On Hot Water Storage Tank

On an inspection today the building has hydronic heating (radiant floor heat at the main level slab and hot water baseboard heat upstairs). A gas-fired boiler provides hot water for heating and for domestic hot water (which is stored in a hot water storage tank).

A connection near the top of the hot water storage tank is labeled "HOT" and "T&P". The TPR valve is located at the end of a pipe connected to the tank at this location and the domestic hot water supply pipe tees off this pipe. (See photo.)

Is this the proper configuration for a hot water storage tank? The TPR vavle should be able to detect excess pressure at that location but I'm wondering how well it will detect high water temperature inside the tank. Does the TRP valve have an extra long probe that extends into the storage tank? If so, what should I be looking for to make sure the correct TPR valve was used?

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The TPR valve could have a long probe, they come in an 8" version. You can't really tell just by looking at them once they are installed as far as I know.

http://media.wattswater.com/PG-TP-ASME.pdf

Watts model number chart and specifics are on-line here.
Probe must immersed in the top six inches of the tank to function as a temperature relief valve.
Not sure if boilers with remote storage tanks require the same as water heater storage tanks since I never see these.

The "tee", shutoff valve and extension to the originally factory installed Long element TPRV are incorrect if it is an indirect fired tank, in opposite to the listing instructions, an unapproved modification, not compliant with the codes or the listings, and unsafe re-design of both appliance and the system(s) involved.Attached pdf includes various examples of correct installations.

If there is an intermediate indirect fired tank, and this is a storage only tank such as a SuperStor CB or GL, then it would almost be correct, but the shut off valve must be after the tee on the hot outlet to fixture side of same and a fair distance away, not before the relief valve - and the piping extension from the tank becomes an extension of the storage potable area, uses a different relief valve.

Master Plumber or Boiler professional may be required to review, photo quality dark, etc. unable to determine from limited viewpoints and contrast, etc..

As you have the originals, and were there, See top of page 8 of 12 of the attached pdf from manufacturer, if there was an intermediate indirect and this is a storage only tank (suspected, but cannot make out top of tank or see side identification and rating label in its entirety).

Hope you find the attached helpful.

Originally Posted by H.G. Watson, Sr.

The "tee", shutoff valve and extension to the originally factory installed Long element TPRV are incorrect if it is an indirect fired tank, in opposite to the listing instructions, an unapproved modification, not compliant with the codes or the listings, and unsafe re-design of both appliance and the system(s) involved.Attached pdf includes various examples of correct installations.

If there is an intermediate indirect fired tank, and this is a storage only tank such as a SuperStor CB or GL, then it would almost be correct, but the shut off valve must be after the tee on the hot outlet to fixture side of same and a fair distance away, not before the relief valve . . .

Not sure what you mean by "in opposite to the listing instructions". It is a SuperStor Indirect Fired Water Heater (not a hot water storage tank as I originally said). I don't know if it is a model CB or GL but I have included a photo of the data plate so maybe you can determine if it is one of those models. It is the only water heater and there is no other storage tank.

My inspection was not for a building inspection but instead was for a simple (Level I) energy audit. The building is a community center for a small development. They plan to install solar water heating and must have a Level I energy audit so they can get a 50% rebate from the state. My inspection of the boiler and water heater were very basic for this energy audit. I was curious about the TPR valve installation. The TPR valve on the boiler is leaking and I am recommending the boiler be serviced. I will also recommend the boiler technician inspect the indirect water heater and its TPR valve.

Thanks for the input.

Originally Posted by Scott Patterson

The TPR valve could have a long probe, they come in an 8" version. You can't really tell just by looking at them once they are installed as far as I know.

I believe the long ones have model numbers which end in 'L' for 'Long'.

Originally Posted by Bruce Breedlove

Not sure what you mean by "in opposite to the listing instructions". It is a SuperStor Indirect Fired Water Heater (not a hot water storage tank as I originally said). I don't know if it is a model CB or GL but I have included a photo of the data plate so maybe you can determine if it is one of those models. It is the only water heater and there is no other storage tank.

My inspection was not for a building inspection but instead was for a simple (Level I) energy audit. The building is a community center for a small development. They plan to install solar water heating and must have a Level I energy audit so they can get a 50% rebate from the state. My inspection of the boiler and water heater were very basic for this energy audit. I was curious about the TPR valve installation. The TPR valve on the boiler is leaking and I am recommending the boiler be serviced. I will also recommend the boiler technician inspect the indirect water heater and its TPR valve.

Thanks for the input.

Models CB and GL are model numbers for storage tanks, not indirect fired water heaters, as I indicated, and you quoted. As you last said, and as evidenced from your latest photos this is indeed an indirect fired water heater. Model SSU-45 to be precise. It is not plumbed correctly at the TPRV port.

In opposite as in: against, not in concert with, opposed, against; the instructions, the Standards, the listings/approvals; against safe practices and the code(s).

It is not plumbed correctly. The TPRV supplied by the factory and installed already as a "long" one directly into the port designed for same so as to extend unencumbered into the storage vessel area. The hot output is lower and several inches offset on the Ultra (but well above the coil input and outputs) see diagram and instructions attached.

Hope you find the attached helpful, it is the Installation Manual for the SS and SSU's.

Looks like a failed attempt at hot water recirc.

The ball valve on the hot side is isolation only and does not inhibit the tpr at all.

Originally Posted by David Bell

The ball valve on the hot side is isolation only and does not inhibit the tpr at all.

You don't get it. I'm not going to argue the obvious with you regarding the incorrect plumbing of this indirect.

The potable hot outlet is plugged and not being used as it should be. The TPRV port has been incorrectly plumbed and modified.

Additionally the TPRV drain is touching the potable cold inlet and its route interferes with the operation of the cold valve. Full bore open valve is required at the inlet location.

Just so you are aware, the domestic hw outlet on an ssu-45 is 46" above the floor. The area you circled is for a control.
The following is from the manual for the ssu-45

Use both thread tape and pipe dope, and connect an NPT brass tee. In the run of the brass
tee, install an NPT brass T & P valve long element, for hot water storage tanks (Required by
local codes, but not less than the valve certified as meeting the requirements for relief valves
for hot water heaters (ANSI Z212B-1984), by a nationally recognized lab that maintains periodic
inspection of production listed equipment. Make sure that the relief valve is sized to the
BTU/Hour capacity and storage capacity of the water heater. The temperature and pressure
relief valve must be plumbed down so discharge can exit only 6” above, or at any distance

below the structural floor; and cannot be in contact with any live electrical parts