# My water heater’s relief valve is dripping. Cause for concern? **URL:** \ **Category:** Factual Questions\ **Created:** [April 9, 2021, 1:16am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639 "2021-04-09T01:16:44Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [April 9, 2021, 1:16am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/1 "2021-04-09T01:16:44Z")
I have an electric water heater and hot water is dripping from the relief valve, down the pvc drain pipe, into the pan, and down the drain. The heater is turned all the way up. Yes, I know that’s not recommended but it’s just me and my wife in the house. We have a large spa tub and filling it with hot water helps relieve her pain from rheumatoid arthritis. Setting it on a lower temperature is not an option. I lost that fight. Is this dripping normal for a water heater on high or is it indicative that I should take some currently unknown action? ---
**Author:** ![FinsToTheLeft](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/finstotheleft/32/2930_2.png) [@FinsToTheLeft](https://boards.straightdope.com/u/FinsToTheLeft)\ **Post date:** [April 9, 2021, 1:49am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/2 "2021-04-09T01:49:32Z")
There are only three possibilities - the pressure is too high, the water is too hot, or the TPV is leaking. Some times a bit of scale makes its way into the valve and it sticks open. Try opening the valve carefully to discharge a quart of water or so and see if it stops. Also if you have an expansion tank hit it to see if it’s empty as it should be. If not, the expansion tank has failed. ---
**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:** [April 9, 2021, 1:59am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/3 "2021-04-09T01:59:01Z")
With my limited, but on hand practical knowledge, Fins has covered it. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [April 9, 2021, 2:03am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/4 "2021-04-09T02:03:44Z")
Agreed. Plus … An elderly TPV may be leaking because the pressure is too high for its aged condition, even though it’s not too high for the HWH itself nor for a shiny new TPV. So you might solve your problem just with a new TPV. Which is real cheap & easy. OTOH, most HWH are only good for about 10 years before they’re a rust-bucket internally waiting for an inopportune moment to split open. So if the HWH is approaching end of life you might do as well to replace it _before_ it tries to flood your house on a Saturday morning when plumbers charge double-time. A new one will be more efficient as well, both due to technical improvements and due to not being full of accumulated gunk that interferes with heating and reduces water capacity. ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [April 9, 2021, 2:18am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/5 "2021-04-09T02:18:24Z")
> [@FinsToTheLeft](#): > > There are only three possibilities - the pressure is too high, the water is too hot, or the TPV is leaking. Some times a bit of scale makes its way into the valve and it sticks open. Try opening the valve carefully to discharge a quart of water or so and see if it stops. > > Also if you have an expansion tank hit it to see if it’s empty as it should be. If not, the expansion tank has failed. - Thanks. I’ll give it a try and report back. We do have very hard water. I had a softener installed about 2 years ago when we bought the house but the heater is original to the house, about 10 years old. I don’t have an expansion tank. ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [April 9, 2021, 2:22am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/6 "2021-04-09T02:22:36Z")
> [@LSLGuy](#): > > Agreed. Plus … > > An elderly TPV may be leaking because the pressure is too high for its aged condition, even though it’s not too high for the HWH itself nor for a shiny new TPV. So you might solve your problem just with a new TPV. Which is real cheap & easy. > > OTOH, most HWH are only good for about 10 years before they’re a rust-bucket internally waiting for an inopportune moment to split open. So if the HWH is approaching end of life you might do as well to replace it _before_ it tries to flood your house on a Saturday morning when plumbers charge double-time. A new one will be more efficient as well, both due to technical improvements and due to not being full of accumulated gunk that interferes with heating and reduces water capacity. - I’ve definitely thought about preemptively replacing it considering that it’s 10 years old. I considered replacing with a gas tankless system but the cost was going to be around $3500 and I’ve heard stories about how long it takes to get hot water from the opposite side of the house as it would in my case. But that’s all material for a different thread which I think I’ll start in IMHO. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [April 9, 2021, 2:26am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/7 "2021-04-09T02:26:32Z")
Here’s a current thread on the topic of slow hot water, long pipe runs, etc. You might gain from this one, or piggyback onto it. > [@Plumbing for hot water](https://boards.straightdope.com/t/plumbing-for-hot-water/939503): > > In my old house, getting hot water in the bathroom upstairs took a long time. I presume that best practices is to split the pipe from the water heater and send one pipe directly to the upstairs bathroom so you can have a nice shower, one pipe goes to the kitchen and from there. I think that my old house had like one pipe that went all around, which might save on buying pipe but is annoying for getting hot water where you want when you want it. This is silly, but my sweetheart and I disagree on w… ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [April 9, 2021, 2:34am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/8 "2021-04-09T02:34:12Z")
Thanks. I’ll take a look. Here in Oklahoma, must plumbing, mine included, is run through the slab so running a new line would have to go through the attic. I’m not quite sure how I feel about that. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 9, 2021, 2:35am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/9 "2021-04-09T02:35:54Z")
Once it starts to leak it will probably keep leaking and the leak will get worse over time. Best to replace it. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [April 9, 2021, 2:37am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/10 "2021-04-09T02:37:22Z")
> [@Nars\_Glinley](#): > > … Here in Oklahoma, must plumbing, mine included, is run through the slab so running a new line would have to go through the attic. I’m not quite sure how I feel about that. … No requirement to run new or additional lines to have quick hot water. Look at my post for a decent explanation of how one system works. Admittedly the energy cost for continuous hot water for pipes embedded in your slab may be high, especially in winter. Then again OK should have fairly low energy prices as befits a conservative petro-state. > [@TriPolar](#): > > Once it starts to leak it will probably keep leaking and the leak will get worse over time. Best to replace it. This. The dripping valve will probably deteriorate pretty quickly unless you’re lucky and it’s just a chunk-o-gunk stuck in it as @FinsToTheLeft suggested. ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [April 9, 2021, 6:54am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/11 "2021-04-09T06:54:51Z")
> [@Nars\_Glinley](#): > > . I don’t have an expansion tank. I don’t know American plumbing. But in this country, where nobody has an expansion tank, and everybody has a reverse flow valve, the relief valve drips each time the tank goes from cold to hot. That’s what it’s there for. The water in the tank gets bigger when it gets hotter. It’s only a worry if it keeps dripping after the tank is hot. Also, in this country, after 10 years one of the options is to replace the sacrificial anode. If you do that, the tank is good for another 10-20 years. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 9, 2021, 10:33am UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/12 "2021-04-09T10:33:36Z")
Most hot water heaters here in the US have an expansion bladder inside the tank. ---
**Author:** ![jjakucyk](https://avatars.discourse-cdn.com/v4/letter/j/3d9bf3/32.png) [@jjakucyk](https://boards.straightdope.com/u/jjakucyk)\ **Post date:** [April 9, 2021, 1:37pm UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/13 "2021-04-09T13:37:34Z")
> [@Melbourne](#): > > I don’t know American plumbing. But in this country, where nobody has an expansion tank, and everybody has a reverse flow valve, the relief valve drips each time the tank goes from cold to hot. That’s what it’s there for. The water in the tank gets bigger when it gets hotter. In the US it used to be common to have no expansion tank and no reverse flow (check) valve. That worked fine as the excess pressure from heating the water would just “back up” the cold water line. As check valves and/or pressure reducers are added by the water company, then the water heater either needs an expansion tank or the relief valve is going to spurt. Any water coming out of the water heater is considered abnormal. > [@TriPolar](#): > > Most hot water heaters here in the US have an expansion bladder inside the tank. I’ve never heard of such a thing. It would be impossible to repair/replace/recharge like you can with an external expansion tank. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [April 9, 2021, 4:10pm UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/14 "2021-04-09T16:10:01Z")
> [@jjakucyk](#): > > I’ve never heard of such a thing. It would be impossible to repair/replace/recharge like you can with an external expansion tank These apparently didn’t catch on like I thought. I should have checked on this, I haven’t seen anything about them since the 80s. I suppose the problem you mention made it impractical, shortening the life of the water heater. ---
**Author:** ![FinsToTheLeft](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/finstotheleft/32/2930_2.png) [@FinsToTheLeft](https://boards.straightdope.com/u/FinsToTheLeft)\ **Post date:** [April 9, 2021, 10:33pm UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/15 "2021-04-09T22:33:03Z")
> [@jjakucyk](#): > > e never heard of such a thing. It would be impossible to repair/replace/recharge like you can with an external expansion tank. My water heater doesn’t have an expansion tank, but my boiler for home heating does. If the tank is full of water the bladder is shot and you replace the whole tank. ---
**Author:** ![Nars\_Glinley](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/nars_glinley/32/8177_2.png) [@Nars\_Glinley](https://boards.straightdope.com/u/Nars_Glinley)\ **Post date:** [April 12, 2021, 8:10pm UTC](https://boards.straightdope.com/t/my-water-heater-s-relief-valve-is-dripping-cause-for-concern/939639/16 "2021-04-12T20:10:58Z")
Working the relief valve has definitely made a difference. It was dripping a pretty good stream of hot water. Now, there’s just the occasional drip of cold water. Thanks everybody.