Thread: No TPR

This is an old on demand water heater for a hot tub. I think it should have a TPR plumbed into the line, but there was none?

Anyone else agree or disagree?

Originally Posted by Jim Robinson

This is an old on demand water heater for a hot tub. I think it should have a TPR plumbed into the line, but there was none? Anyone else agree or disagree?

Pressure relief is required on tankless. Temperature and pressure relief combination is not.

P2803.1 Relief valves required.

Appliances and equipment
used for heating water or storing hot water shall be protected
by:
1. A separate pressure-relief valve and a separate temperature-
relief valve; or

2. A combination pressure- and temperature-relief valve.

I have never seen a TPR or PR valve on a pool or spa heater... never thought about it though. Was this system closed or operated under pressure with potable water or an open vessel heater like for a pool?
I can't prove it but I would think that heaters on open vessels would be under a different section of the code... any help out there on this?

That was kind of what I was thinking. It is a closed system, so there is no connection to the water lines for the rest of the house. It still seems like if the thermostat failed on the heater and the pump wasn't on to circulate the water, the pressure would probably blow the connection lines. I think it would be better if the pressure were controlled and directed with a relief valve.

Of three gas heated hot tubs that I've seen, only one was actually operable,and I can't remember if that had a relief valve or not.

Originally Posted by Jim Luttrall

I have never seen a TPR or PR valve on a pool or spa heater... never thought about it though.

All pool and spa heaters in South Florida have required T&P relief valves for decades.

The Florida Building Code, Residential also requires T&P relief valves at all water heating appliances.

The 1994 Standard Plumbing Code required T&P relief valves at all storage water heaters operating above atmospheric pressure have T&P relief valves but exempted instantaneous type water heaters, however, the 1997 Standard Plumbing code removed the latter exemption as those types still operate 'above atmospheric pressure' and can cause problems.

The IRC requires T&P relief valves for appliances "used for heating water or storing hot water" and the on-demand instantaneous types are "used for heating water", whenever you heat water you raise the pressure of the water and risk raising the pressure and temperature too high.

Originally Posted by Jim Robinson

Of three gas heated hot tubs that I've seen, only one was actually operable,and I can't remember if that had a relief valve or not.

I could probably count on one hand the number of T&P relief valves installed for pool and spa heater which were not stuck shut and/or otherwise not working ... excepting brand new installations within the first year warranty.