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Is it ok to have a bucket under temperature/pressure relief valve, rather than drain outside?

MichaelBa | Posted in General Questions on

Hello,

I am waiting to get my 30 gallon electric water heater installed. It is placed inside the bathroom , right next to the shower.

I would like to avoid running the valve through my floor or outside the wall, so am wondering if it is safe/common to just place a bucket underneath? According to this lowes tutotorial, it is : https://www.lowes.com/projects/repair-and-maintain/install-an-electric-water-heater/project

I have a few questions regarding this
1) How often does the t/p valve drain and how much water is expected? In other words, is a 5 gallon bucket more than enough as long as it’s emptied regularly? Any chance that more than 5 gallons will come out?
2) I will have an expansion tank. Will that help with minimizing the amount of water dripped from the valve?
3) Does water ever drip out of the drain valve or is that simply there just to drain the tank manually? If not, what is the pirpose of the pan?
4) What would cause a the temp valve to constantly run out water (until the shutoff valve is turned)?

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Replies

  1. this_page_left_blank | | #1

    Interesting questions. From what I've seen, it's pretty common to have nothing connected to the pressure relief valve. Probably not wise, but common nonetheless. In my 44 years, I've never seen nor heard of one of these valves activating. I'd say it's not actually expected to happen, but it's there to cover a what-if scenario. I have no idea how much would come out if it went off, it depends on what is causing the over pressure and whether it's an ongoing situation.
    The drain is there to drain it manually, it should not drip. The pan is to capture water in case of a tank leak. That's another thing that is commonly not even there.

  2. Expert Member
    MALCOLM TAYLOR | | #2

    Michaelba,

    I guess the first thing to bring up is that most codes require the pressure release valve to be installed so its discharge is directed to a floor drain or pan, and insurance companies generally frown on non-code installations.

    if that isn't an issue for you then it's a question of how risk adverse you are. If the valve opens because of excessive water temperature, then a lot of water can be discharged before the valve closes. If it opens because of a pressure problem there is typically a lot less. Perhaps most pernicious are the slow leaks from defective values. They could easily fill the bucket and overflow for a considerable length of time, but at a slow rate.

    The most common cause of water heater replacements are leaks developing within the jacket at the elements, intake, outlet or drains. Installing one without a pan is just a really bad practice.

  3. this_page_left_blank | | #3

    How risky it is depends on the location of the tank. If it's in an unfinished basement with a floor drain two feet away, I personally would not worry about either a pan or a hose. But as pointed out, code will almost certainly say you need them no matter what. I just looked at the Lowes link, and I would not consider that in any way official installation instructions. I suspect the manual for the tank is going to say the same as the code. Do you really want to see a Lowes bucket on the floor of the bathroom every time you go in there?

  4. walta100 | | #4

    It is unlikely but possible for the valve to open fully and flow much like a garden hose with boiling hot water.

    A 5 gallon bucket would last less than a minute.

    The idea is for T/P valve to drain somewhere you will notice the flow and the water will not damage the home much.

    Walta

  5. ohioandy | | #5

    Where I am these heaters sometimes fail catastrophically as the bottom literally disintegrates into rust. It seems more common when the unit is in a damp basement, worse when it's resting on a damp floor. But the catastrophe is preceded by an extended period of leaking, and as Walter said, the pan is there to help you notice the leaking, whether it's from the tank or an element or a plumbing hookup. Cheap insurance.

  6. severaltypesofnerd | | #6

    California requires the TPR end up outside.
    However, in retrofit it's OK to have it end up in a pan, as long as the pan has a water alarm.

    Or use something like the Watts LF210 -- which is replaces the temperature portion of the TPR, shutting off the gas if the temperature gets too high. Then you can place the pressure relief portion of the TPR elsewhere in the plumbing system.

  7. Expert Member
    Peter Engle | | #7

    The TPR valve is there to prevent the water heater from exploding. If the gas valve doesn't shut off properly and keeps heating the tank, eventually the water will expand into steam. When the valve opens to vent the steam, it is dramatic. The pressurized hot water flashes into steam instantly and violently. This is why the codes require a rated extension pipe extending from the TPR down to within a foot of the floor. If not, someone standing near the valve when it opens could get severely scalded. The extension pipe must be directed generally downhill - no uphill jogs - so that water doesn't plug the pipe and prevent the steam from expanding properly. If you have a bucket under the pipe, it cannot be taller than the pipe opening for the same reason. That much is for primarily safety reasons.

    If the water tank is located above finished surfaces (floors, or a finished area below), that's when it needs a pan to protect against leaks. The TPR can be directed into the pan or outside the house. The pan should have a drain directed outside the house. If you use only a bucket or a pan without a drain, a leaking tank or TPR will simply fill the bucket or pan and overflow. Either one can cause a LOT of leakage quickly.

    For video of the Mythbusters testing a water heater to failure, go here:
    https://www.youtube.com/watch?v=rGWmONHipVo

  8. user-5946022 | | #8

    Great info Peter. You noted the T&P valve pipe must be within a foot of the floor, but also noted it can be directed to the water heater pan. What if the water heater is on a pan, and the pan is on a stand 18" off the floor? Would it be ok for the T&P valve pipe to direct to the top lip of the pan, near the back of the water heater (the the tank would be between the overflow and any person)? This is presuming the pan is then piped to the exterior. If this is ok, would it also be ok for the pan drain to have a trap on the end of it, filled with alcohol so it does not freeze, for the purpose of eliminating a 1/2" hole to the outside?

  9. Expert Member
    Peter Engle | | #9

    Yes, if the water heater is on a platform, the pipe can terminate near the platform rather than the floor. Turning the water heater so the drain pipe is towards the rear is nice, but not required. The pan drain can have a trap, but the TPR pipe cannot. Alcohol might not work well to seal the trap, as it evaporates pretty quickly. Keep the trap inside the copnditioned space, fill the trap with water and float a tablespoon of vegetable oil on top. Or, use non-toxic antifreeze (RV antifreeze) to fill the trap.

  10. tommay | | #10

    If for any reason the T& P should open it should only disperse a pint or so. If it does open you should check your temperature setting. Manually opening the valve by lifting the lever should be done occasionally to ensure it is clean and shuts off properly. If you find there is water leaking out it is because either the water is to hot and hot water vapor is coming out or the seal is starting to fail. If it is the former, turn down the temp, if it is the latter, replace it.

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