# Hot water heater help **URL:** \ **Category:** In My Humble Opinion\ **Created:** [February 7, 2018, 1:37pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356 "2018-02-07T13:37:52Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![Loach](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/loach/32/350_2.png) [@Loach](https://boards.straightdope.com/u/Loach)\ **Post date:** [February 7, 2018, 9:24pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/21 "2018-02-07T21:24:31Z")
> [@Turble](#): > > Somebody’s gotta say it – might as well be me. It’s not a hot water heater – it’s a water heater. You don’t need to heat hot water. > > BTW & FWIW, I had the very same problem once, years ago. Expansion tank did the trick. It’s a heater that makes hot water and not hot air or pudding. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [February 8, 2018, 1:27am UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/22 "2018-02-08T01:27:35Z")
> [@carnivorousplant](#): > > Let’s go for “[essentially incompressible](https://water.usgs.gov/edu/compressibility.html)”. > > Your example says that for each Celsius degree that water is heated, it expands by .02%. > [@carnivorousplant](#): > > From 4 C to 100 C, when it boils, water will expand by 100(.02) = 2%. I’ve had to disconnect old electric water heaters for whatever reason … flip them back on in a few days and every once in a while it will bust the old weak tank … so water does expand some when heated … no such thing as a perfect incompressible fluid, just some liquids are as close to incompressible as to make no difference … This is a new tank … so, I agree this isn’t the problem … I might try to open the valve for a bit and see if that doesn’t flush out a bit of dirt or calcium deposit that might have gotten stuck in there … next I’d replace the pressure relief valve … then the burners … if none of that worked I’d shoot it with a 30-06 and get a new tank … ---
**Author:** ![Morgenstern](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@Morgenstern](https://boards.straightdope.com/u/Morgenstern)\ **Post date:** [February 8, 2018, 5:55pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/23 "2018-02-08T17:55:41Z")
Are you sure that all the solder joints are soldered all the way around the fittings? Even the factory soldering? ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [February 8, 2018, 6:12pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/24 "2018-02-08T18:12:13Z")
> [@watchwolf49](#): > > I might try to open the valve for a bit and see if that doesn’t flush out a bit of dirt or calcium deposit that might have gotten stuck in there … next I’d replace the pressure relief valve … My FIL maintained that the PRV was a one shot deal, that once it opened up it was unusable. Perhaps he was being careful. ---
**Author:** ![Doctor\_Jackson](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/doctor_jackson/32/32_2.png) [@Doctor\_Jackson](https://boards.straightdope.com/u/Doctor_Jackson)\ **Post date:** [February 8, 2018, 7:07pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/25 "2018-02-08T19:07:41Z")
> [@carnivorousplant](#): > > My FIL maintained that the PRV was a one shot deal, that once it opened up it was unusable. Perhaps he was being careful. I think that is a “used to be” kind of thing, as I always heard the same from my dad. [This site](http://www.watts.com/pages/support/tp.asp?catId=64), however, says: > [@](#): > > WARNING: Following installation, the valve lever MUST be operated AT LEAST ONCE A YEAR by the water heater owner to ensure that waterways are clear. Certain naturally occurring mineral deposits may adhere to the valve, blocking waterways, rendering it inoperative. When the lever is operated, hot water will discharge if the waterways are clear. Further, regarding thermal expansion, the same site says: > [@](#): > > Thermal Expansion: When water is heated it expands. In a 40 gallon water heater, water being heated to its thermostat setting will end up expanding by approximately 1/2 gallon. The extra volume created by this expansion has to go somewhere or pressure will dramatically increase, such as when water is heated in a closed system. > A good indication of thermal expansion is when the T&P valve releases about one cup of water for each 10 gallons of heater capacity with each heating cycle. A half gallon expansion in a 40 gallon tank represents a tiny percentage, but adding an excess 1/2 gallon of incompressible liquid to a closed system can lead to catastrophic failure. I would first check the temperature setting to make sure it is not set too high. Next step is to check water pressure coming into the heater to make sure it is not excessive (\>75lbs). If the temp setting and incoming pressure are OK, next step would be to add an expansion tank. If that doesn’t work, sell the thing to Elon Musk as a potential rocket booster 🙂 ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [February 8, 2018, 7:43pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/26 "2018-02-08T19:43:39Z")
Thanks, Doctor. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [February 8, 2018, 9:54pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/27 "2018-02-08T21:54:52Z")
If the pressure in the tank became greater than the water pressure feeding it would it not simply push back out into the water system feeding it? With a check valve I know it wouldn’t but I wasn’t aware that water heaters had check valves. Sometimes pressure relief valves can have a piece of debris stuck in the during manufacture activating them for just a quick shot will dislodge anything that might be in the seal. Not sure if your can be activated. ---
**Author:** ![johnod](https://avatars.discourse-cdn.com/v4/letter/j/dc4da7/32.png) [@johnod](https://boards.straightdope.com/u/johnod)\ **Post date:** [February 9, 2018, 3:22pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/28 "2018-02-09T15:22:20Z")
Replace the relief valve, it’s faulty. Happens fairly often, especially if someone opens it needlessly. So don’t do that. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [February 11, 2018, 1:51am UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/29 "2018-02-11T01:51:15Z")
> [@johnod](#): > > Replace the relief valve, it’s faulty. > Happens fairly often, especially if someone opens it needlessly. > So don’t do that. I think needlessly is the key word here, his valve is already leaking so it is not needlessly. I spent the better part of my life working with various types of pressure relief valves and I have found that on occasion they need to be reseated to blow out a contaminate. If it doesn’t work he has lost nothing, if it works problem solved. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [February 11, 2018, 2:02am UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/30 "2018-02-11T02:02:39Z")
> [@HoneyBadgerDC](#): > > I think needlessly is the key word here, his valve is already leaking so it is not needlessly. I spent the better part of my life working with various types of pressure relief valves and I have found that on occasion they need to be reseated to blow out a contaminate. If it doesn’t work he has lost nothing, if it works problem solved. I’ve installed and assisted in installing water heaters, and I have always been afraid of being parboiled by the PRV. The pipe on the end of our water heater PRV ends right over a floor drain in the laundry room. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [February 11, 2018, 2:30am UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/31 "2018-02-11T02:30:15Z")
> [@carnivorousplant](#): > > I’ve installed and assisted in installing water heaters, and I have always been afraid of being parboiled by the PRV. The pipe on the end of our water heater PRV ends right over a floor drain in the laundry room. I agree they can be dangerous if very hot water is coming out even under normal water pressure. Caution has to be used. ---
**Author:** ![ZurBob](https://avatars.discourse-cdn.com/v4/letter/z/71e660/32.png) [@ZurBob](https://boards.straightdope.com/u/ZurBob)\ **Post date:** [February 11, 2018, 3:58am UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/32 "2018-02-11T03:58:28Z")
It’s entirely possible your PT valve is functioning properly. Perhaps your new thermostat is defective (heating the H2O too high) causing the PT valve to open. Turn your temperature setting down some. BTW… If the old heater (PT valve) functioned OK without an expansion suppressor, your new heater should also be OK without one. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [February 11, 2018, 1:18pm UTC](https://boards.straightdope.com/t/hot-water-heater-help/808356/33 "2018-02-11T13:18:34Z")
Water pressure varies throughout different parts of the day. At night it tends to be higher as less people are using it. His PR valve may only be leaking at peak water pressure times. This would explain intermittent leaking. [Previous page](https://boards.straightdope.com/t/hot-water-heater-help/808356.md?page=1)