Look here for a Water Heater Blast!

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Reference Only:

**422.47 Water Heater Controls. **

All storage or instantaneous-type water heaters shall be equipped with atemperature-limiting means in addition to its control thermostat to disconnect all ungrounded conductors. Such means shall comply with both of the following:

(1) Installed to sense maximum water temperature.

(2) Be either a trip-free, manually reset type or a type having a replacement element. Such water heaters shall be marked to require the installation of a temperature and pressure relief valve.

*Exception No. 1: Storage water heaters that are identified
**as being suitable for use with supply water temperature of *82°C (180°F) or above and a capacity of 60 kW or above.

*Exception No. 2: Instantaneous-type water heaters that **are identified as being suitable for such use, with a capacity *of 4 L (1 gal) or less.

FPN: See ANSI Z21.22-1999/CSA 4.4-M99,

*Relief Valves *for Hot Water Supply Systems.

thanks for sharing that, OMG!


It’s probably not a bad idea to flip the pop off valve open every once in a while to be sure it isn’t corroded shut. Just be aware it may stick open when you do.
My water heater is outside so that is not that big a deal. I bet you folks up in the frozen north don’t have that option. :wink:

" Such water heaters shall be marked to require the installation of a temperature and pressure relief valve."

Marked by whom. Code inspectors?

We are not code inspectors.



A. Water Heaters: UL 174, energy-efficient, fully automatic.

  1. Water Heaters: Type(s) and size(s) indicated, specified, or scheduled with necessary accessories
    for complete installation ready for operation.
  2. Tapping for Hot and Cold Water: 20 mm (3/4 inch) NPT minimum.
  3. Thermostats: Interlocked so that only one heating element may be operative at any one time.
  4. When required to meet warranty requirements, provide anodic rod.
  5. Safety Pressure and Temperature Control Valves: ANSI Z21.22.
  6. Heaters: 230 volt, 60 cycle current.
  7. Heaters: NEC (ANSI/NFPA 70) for hard wire connections to service wiring.
  8. Water Heaters: Bear UL label.
  9. Water Heaters: Certification by accredited independent testing laboratory that water heater is
    properly labeled and is in compliance with ASHRAE/IES 90.1 and 90.1b when tested in accordance with
    DOE test procedures in 10 CFR, Part 430.

Will you may not be a code inspector but you are a safety inspector in the sense that you should be pointing out safety related defects. Joe is pointing out that the water heater was marked to say it requires a relief valve. In fact it will be sold with one built in. For the home inspector, you should look to see if it is still there and that nobody screwed a pipe plug in the outlet because it was leaking. I think it is opening yourself up to some liability if you operate it, since it might start leaking after that … assuming the homeowner never tests it. Trick the homeowner into doing it :wink:

This guy says test them


Barry says no. I would never test one for a client, nor have I ever tested one at my house. I also have not tested the airbags in my car.

They are few and far between that don’t leak after you test them. Especially on a hot water boiler.

It really depends on your water quality and how often you test. I used the pop off like a hot water faucet to fill mop buckets and such in Md, never having a problem but they had better water than I do here. I still try to check mine every now and then here. I did have had to replace it once because it dripped afterward.

In some localities it was and or still is permissable to direct the piping from the TPT upwards into the attic or roof before exiting the dwelling. This is usually done in older residences that originally had no TPT line installed to the outside and later had new heaters installed in utility rooms with no outside walls.
There is supposed to be a drain valve located in these lines right at the low point. This valve should be periodically opened to check if the TPT is leaking. Also, if you should open the TPT and fail to drain the line afterwords, water will sit on the pressure spring of the TPT and corrode it to the point where it fails. I would say it is risky business to open any valve on a water heater except for the drain valve on the TPT line. If you ever plan to open the tank drain for any reason other than tank replacement, be prepared with a threaded hose cap and washer since it will probably drip afterwords.

this info is from a boiler plate item on the INspectVue software… I was hoping for some more detailed requirements. 9/10 of the electrical hot water heaters have standard romex wiring… nothing armored.

thanks in advance.

Substandard wiring was found for the water heater’s power supply. This is both a fire and a shock hazard. Recommend having a qualified, licensed electrician evaluate and make repairs as necessary. Typically, electric water heater power supply wires require flexible, armored “BX” conduit, bushing(s) and possibly a covered junction box.

Thanks, and I will ad that the supply to a water heater often was required to be not less than 105 degrees C, so that the insulation would be able to withstand temperatures.

Sometimes a “whip” will be used from a J-Box with that higher rated wire.

Why would you need 105c wire in a water heater. The heater usually trips the top thermostat overload when it gets much over 140f/60c
I looked at mine and there is no labelling to indicate this.

I know you usually need 105c on range and oven whips. That is why they are usually factory installed.


I remember long ago 1969 when I was an Assistant Electrical Inspector in New Haven, Connecticut where I saw the label at the splice compartment calling for 105 degrees C wire:

I thought that we could look at the history of UL
UL milestones in product safety certification and UL’s contribution to advancement of new technologies

Click on the appropriate time period below for more information.