enter image description hereWater has come out of the PVC pipe attached to the hot water heater in the garage (less than a cup of liquid). There's no drain under the PVC pipe, so it seems it's not intended that it would drain a large amount of water (or often). We've never seen water leak there... but for the last couple of days there has been water that has leaked. (The pipe is ONLY attached to the water heater, so this is not HVAC condensation.)

The water heater is about 4 years old. Is this normal (and just hasn't happened or been noticed before) -- or should we call a plumber because it's the precursor to a major leak or overflow valve issue? Thank you!

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  • Can you upload a picture showing where the pipe attaches to the water heater? What model is the water heater? Dec 23, 2021 at 4:19
  • 1
    I posted a pix of where the PVC attaches. The water heater is a "Smith - Proline Commercial Grade" 50-gallon water heater.
    – Tonya Long
    Dec 23, 2021 at 4:29
  • Is there an expansion tank attached to your water heater? If not, this would almost certainly happen
    – Matthew
    Dec 23, 2021 at 7:18

3 Answers 3


The pressure relief valve on a hot-water tank is meant to relieve pressure to prevent damage to the tank. It is needed for a few reasons, e.g.,

  • The water tank holds a large volume of water. If the water inside actually boils (e.g., a thermostatic switch fails), it might explode if there were no relief valve.
  • There can be pressure surges in a water main and the valve would open before the (less dangerous, but messy) splitting of the tank.

The valve might have opened because of overheating, but that likely would have released more water. More likely, there was a surge, or water hammer, that spilled a small amount.

Another likely cause of the puddle is deterioration of the rubber washers. The valve is subject to constant immersion in very hot water, so deterioration is faster than in a faucet washer. Although repairing the valve itself is trivial, it requires cooling the tank and partially draining the system, a nuisance -- so if it stopped leaking, just keep an ey on it fo further issues.

Finally, someone might have pulled the test toggle (the silvery handle at the top of the pipe -- good photo, BTW!) accidentally, or out of curiosity (and I've bumped it myself by accident, spilling a cup or so). As mentioned by others, it a good idea to test the valve every year or so, but sometimes it does not shut well afterwards, requiring a quick flip of the lever to reseat it... and sometimes it leaks, afterwards. Have a bucket underneath that overflow!


I see lime marks on the concrete that suggest that small quantities of water waster have been coming from that pipe for more than a few days.

That valve looks like the temperature and pressure relief valve, it is normal for this to produce a small amount of water. Also it should be tested regularly, there should be details on the safety labels on your water heater.

Normally this valve discharges into a drain or onto the ground outdoors, but the building rules may be different at your location.

If your water thermostat fails in the on position, this valve will release large amounts of water


Water expands. In the winter the water entering your hot water tank is cold and once heated the volume of water is a lot larger. When the water expands the pressure increases and if you have an expansion tank the expansion tank temporarily takes this expanded volume, if you don't have an expansion tank or your expansion tank has failed, the increase in volume either comes out the relief, shows up as additional pressure when you turn on the faucet or pushes some water back to the city (depends if you have a backflow or check value between you and the city).

If you don't have an expansion tank you should get one - they are typically a little larger than a basketball. The relief valve is a safety valve it isn't meant to be dumping water all the time and you don't want it to fail.

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