check valve on hot water heater inlet?

[Jules]

Well, our water heater's playing up (I'm suspecting lower element of the pair), but I noticed that there's no check-valve on the cold inlet; should there be? We're on a private well with a pressure tank on the cold side, if it makes any difference. Sometimes the hot water output seems to cough and splutter a bit when the hot tap's first turned on, and I wondered if the lack of valve means that water's somehow getting sucked back out of the tank when "at rest" via the cold line, dropping the tank level below the hot water output.

I discovered yesterday when I went to drain the system that the shut-off valve on the cold water inlet to the heater is utterly buggered - so I need to do some putzing around with a new valve there anyway, and I suppose it'd make sense to add a check-valve if needed at the same time.

Oh, the upper heating element in the tank uncrews nicely. The lower one that I want to change has currently had a 4ft breaker bar put on it and isn't shifting. I'm leaving it to soak in a well-known penetrating oil for a bit before I try again :-)

cheers

Jules

[<me9]

A proper penetrating oil, or a water displacer?

D&RFC.

[Jules]

Heh, you got me. Something that comes in a blue can with a red cap and claims "loosens rusted parts" on the front. I suspect it'll do f*ck all ;)

[fred]

In article , Jules writes

Unless you've got an expansion vessel and a bundle of safety gear round the hot water cylinder then it shouldn't have a check valve on the inlet. As the water is heated it needs room to expand and for a gravity fed system (which yours sort of seems to be) the safe way to allow for this expansion is back up the inlet. If this was a system where the feed tank was shared between more than one property then I doubt that would be allowed over here on ground of possible contamination of the supply in a negative pressure situation.

The spluttering sounds just like dissolved oxygen being released into the top of the cylinder on heating which is normal on a system without a vent.

Don't, unless you're absolutely sure that it is safe to do so.

Breaking these out is a faq, see:

[Jules]

Thanks for that.

OK - will have to look into that, then! It's actually quite violent sometimes when it does it (enough to launch droplets 3 - 4ft from the sink), and a fresh tank of hot water's pretty darn hot right at the top.

I suspect that someone may have not had the washer (or broke it) and has just glued the darn element in.

No joy heating it via a torch, hitting it with a hammer, cold chisel on the edge of the nut, or the trick of trying to tighten a little before loosening. Looks like it'd be a drill-out job, which will be fun. Might just replace the damn thing though as it's pretty scaled-up inside, the drain valve's useless (smaller internal diameter than the size of the pieces of scale that build up - what bright spark designed *that*) and a newer one will probably be more efficient anyway (current one was made in '93)

cheers

Jules