A workaround for electric water heater T&P relief valve discharge

[shanaling]

Our old water heater is not up to code because the temperature and pressure relief valves are not connected to pipes that lead outside.

We do have a pressure valve on the main water line though. Is this good enough for pressure relief?

For temperature, it would be expensive for us to cut through the wall to connect the temperature relief valve to a pipe that leads outside. Is there a workaround? Would connecting the valve to the pipe under the sink work? Or use an electric tankless water heater instead? I believe tankless electric does not require a temperature valve correct?

Thanks!

[zolotiyeruki]

As I understand the codes, the T&P relief valve needs to drain somewhere safe, and it can't have anything in its discharge line that could block it, like a valve.  Our water heater's T&P valve just drains onto the basement floor, eventually leading to the same drain as the furnace, A/C, and water softener.  You'll have to check your local building codes--in our last house, the A/C condenser just drained to the outside of the house, but where we live now, all that water has to go into the sanitary sewer.

[Jon Bon]

So what?

Are you replacing it? Or have some silly city inspector poking his nose where it does not belong?

Unless forces outside your control are forcing you to update it you could probably leave it alone.

But like zolo says, usually tanks are located in the basement, drain right into the floor, which slopes to a floor drain and that is sufficient. Where is your hot water tank located? PVC is super cheap, as long as it goes to a drain (storm or sanitary) I think you are in good shape. The valve letting go is a once in a lifetime occurrence, so I would not sweat it much, the valves can go bad but that is usually just a small leak.

[shanaling]

yes we are replacing ours, and ours is in a cabinet in the kitchen about 40 feet from outside of the house

[sokoloff]

I’ve always seen T&P valves vented to daylight (no other pipes) straight down the side of the heater.

If that then drains into a pan that then drains outside, that’s ok, but you can’t pipe the T&P outlet into other pipes as far as I know or have ever seen.

Electric heaters need a T&P. It’s a fail safe to prevent over-pressurization (making a steam bomb) if the T-stat ever fails such that the heater stays on. Gas, electric, or pure magic as a heat source: they all need this safety device and that device needs to output to daylight, IMO.

[Jon Bon]

Where are you located?

My code book says

PRV Required 09 IRC 2002.4/09 UMC 1011.0
and
PRV Drain piped to within 18 inches of floor or receptor 09 IRC 2002.4 09 UMC 1006.0

The logic here is water all over your floor is MUCH better then a overheated watertank bomb. The PRV should almost never leak water, if it does either the valve or the thermostat has gone bad and need replacement right away. Honestly I think you need to see the water is the idea, so you can take immediate action. So if it was leaking directly into a pipe that went into your plumbing or outside you would not notice it, which would be an even bigger problem.

Who told you it had to be outside? Now that I thought about this that makes zero sense and is actually much more dangerous.

[shanaling]

Im in California.

Pressure and Temperature Relief Drain (“P&T Drain”) to the Exterior – The CA Plumbing Code requires the P&T relief drain to be run to the exterior. This requirement is in place to prevent accidental scalding when the P&T relief is discharging.

[Jon Bon]

Ugh that is super annoying, one of the reasons I dont love 'the code'. Often it would be better/safer/faster to do it a different way, but alas.

My only other advice other then piping it outside would be to get one of those condensate pumps? I doubt even that would be code but it would give you lots of options in how to route the water.

Or you know, just not get a permit. That's common practice where I am, pretty sure you do 15-life in cali for violating the code!

[Penn42]

To make sure you're clear: The T&P valve is the same device.  It almost sounds like you think there will be two separate lines, but there will only be one.

As far as getting it outside, that's something you can do pretty easily.  All it would cost is the cost of the type M copper and getting a little dirty doing the crawl.  I'd cut a hole just larger than the diameter of the pipe in the floor in the cabinet and then run the pope along the bottom of the floor joists until you get to the side of the house.  Poke another hole there, weatherproof both holes with a product of your choice, and voila!  You could even make any necessary turns with a couple sharkbites (which are kinda spendy, but not as much as a plumber!) so you don't have to worry about soldering.  They make a variety of pound in hooks and other sorts of easy to use anchors to fasten the pipe to the joists with.

[BudgetSlasher]

The PRV should almost never leak water, if it does either the valve or the thermostat has gone bad and need replacement right away.

Or a high demand for hot water has significantly dropped the tank temperature and there is a back flow preventer of the water main and no expansion tank is installed. Then when all the taps are closed and the water expands as it heats it can cause the PRV to drip. It can be even worse if the tank in interruptible power during peak demand hours.