Tankless and TRP valve

Are TPR valves needed on tankless water heaters?

good question-----I have found several without even though the installation instructions say they are required. Did you find one without?

I found one with it. It was located on the supply pipe. Pointed up and without the drain line.



I have seen them with-and without.

Looking at various manufacturer spec’s some are not required.

I can not think of a reason not to have one, it is one more safety item.

Weither it is required or not probably depends upon the manufacturer and if another safety device is installed.

In (2) states a relief valve is required…but for the most part unless you are in those states…it is not needed…but is a enhancement in safety.

Thanks JEFF…typo…PR valve is what I was speaking of…See Mr. Zinsco knows PR valves also…EXCELLENT…:slight_smile:


Check out the above link, I install about 40 of them a year…most do not require a relief valve…but you can install them if you wish…but in (2) states the valve is required.

PR (pressure relief) valve? Yes (PR valves are required on most residential supply systems).

TPR (temperature & pressure relief) valve? No.

TPR’s are required only in tanks (boilers and heaters).

What you have pictured is a PR valve.

Here is info from the data plate on the side of a Rinnai heater

TPR 002.jpg

Poloma units made by Rheem have them in the carton when purchased.
Also in the installation instructions on the output side of heater.

Jeff is correct. All tankless manufacturers require the use of a pressure only relief valve system meeting all ANSI and or local codes. The systems are equiped with high limit switchs to handle the excessive heat issue. If you find a system installed without a proper pressure relief valve, I’d write it up as being an Unsafe Condition.

Refer to page #12 of the Takagi installation manual:


Additional IMC Requirements

**SECTION 1006
1006.1 Safety valves for steam boilers. **All steam boilers
shall be protected with a safety valve.
**1006.2 Safety relief valves for hot water boilers. **Hot water
boilers shall be protected with a safety relief valve.
**1006.3 Pressure relief for pressure vessels. **All pressure vessels
shall be protected with a pressure relief valve or pressure-
limiting device as required by the manufacturer’s
installation instructions for the pressure vessel.
**1006.4 Approval of safety and safety relief valves. **Safety
and safety relief valves shall be listed and labeled, and shall
have a minimum rated capacity for the equipment or appliances
served. Safety and safety relief valves shall be set at a maximum
of the nameplate pressure rating of the boiler or pressure
**1006.5 Installation. **Safety or relief valves shall be installed
directly into the safety or relief valve opening on the boiler or
pressure vessel. Valves shall not be located on either side of a
safety or relief valve connection. The relief valve shall discharge
by gravity.
**1006.6 Safety and relief valve discharge. **Safety and relief
valve discharge pipes shall be of rigid pipe that is approved for
the temperature of the system. The discharge pipe shall be the
same diameter as the safety or relief valve outlet. Safety and
relief valves shall not discharge so as to be a hazard, a potential
cause of damage or otherwise a nuisance. High-pressure-steam
safety valves shall be vented to the outside of the structure.
Where a low-pressure safety valve or a relief valve discharges
to the drainage system, the installation shall conform to the

Interesting…not a single one I have installed in VA have a “Pressure Valve” on them that WE would install…to the BEST of my knowledge only (2) states have a Mandatory PRV requirement…but hey…I am a Electrician not a Plumber…:slight_smile:

All of ours are inspected and again not a single one has an “External” PRV installed on them and the local AHJ never has a issue with it as we show him the SETS manual which says it is not required except in the listed states.

However…it is important to note that the SETS units we install have Thermal Relays on the front that POP out and have to be depressed in a situation of a thermal temp overload so to speak…but not a pressure valve…:slight_smile:

Hey Paul,

I always operate under this general assumption. #1 basic rule of the various model codes are for all installations of code related materials and systems meet OEM installation and or operational specifications. Since I don’t do code inspections, and the local building department won’t defend me in a lawsuit, I rarely use them as a basis for safe and or unsafe conditions. All of the tankless water heater companies I’ve encounter mandate the installation and use of an exterior accessible pressure relief valve properly drained by gravity flow down and away from the subject valve.

And most model plumbing codes require a PRV to be installed somewhere on the supply systems of residential dwellings where potable water is provided by a public utility.