My water heater’s relief valve is dripping. Cause for concern?

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?

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.

With my limited, but on hand practical knowledge, Fins has covered it.

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.

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.

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.

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.

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.

Once it starts to leak it will probably keep leaking and the leak will get worse over time. Best to replace it.

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.

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.

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.

Most hot water heaters here in the US have an expansion bladder inside the tank.

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.

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.

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.

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.