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

In article . com, Jules
writes

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.

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.

I suppose it'd make sense to add a check-valve if needed at
the same time.

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

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 :-)

Breaking these out is a faq, see:
http://wiki.diyfaq.org.uk/index.php?...rs#Replacement
--
fred
BBC3, ITV2/3/4, channels going to the DOGs

On Sat, 03 Oct 2009 11:29:07 +0100, fred wrote:
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.

Thanks for that.

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.

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.

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 :-)

Breaking these out is a faq, see:
http://wiki.diyfaq.org.uk/index.php?...rs#Replacement

Urgh. I can't see any sign of a sealing washer on it, unlike the top one -
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