Double Check Valve Or Isolator Valve?

[dinger71uk]

I have a small leak on my HW circuit, it's the return pipe i think at the bottom of the cylinder there is a join where it connects up the hw cylinder to the rest of the HW circuit. My issue is wether this joint is a 22mm isolator valve or 22mm double check valve. ? The bathroom rads are on when hotwater is called for and when heating is on.

The leak is coming from the top screw of the vlave, i have temporarily used metal expoxy over the screw to stem the flow. Looking at the valve there are two letters empossed on the side BB but thats the only distinguishing marks I can find.

Does anyone have any ideas?

 

[hi-spec plumbing heating]

have you a pic.
it could be an iso valve or a check valve.
some times gravity check valves are fitted if the system suffers reverse circulation.
or the bathroom rad could be connected to the hw circuit.

 

[dinger71uk]

heres a diagram of what i think the circuits look like the bathroom rads are def on the same circuit as the hw.

 

[hi-spec plumbing heating]

have you a photo of this valve

 

[dinger71uk]

not with me at the mo but can do when i get home

 

[dinger71uk]

heres the pics hope it helps

 

[spudkey]

its an isolation valve, its too short for a double check and a single check wont have a verification screw

 

[Gasguru]

Looks like a standard "ballofix" type isolating valve. Single check valves don't have test points and double check points (which do) are longer.

Never use a "ballofix" type valve on the heating ...they nearly always leak on the spindle as the O ring fails.

Replace the valve with a lockshield 22mm gate valve or a plain 22 gate valve and remove the wheelhead.

The valve is for balancing (ie throttling down) the hot water circuit and the radiator circuit. ie when the hot water is selected the rads. will still heat up.

 

[chrishutt]

There's something very odd about that connection to the cylinder. I don't think it's the return from the heating coil. If it was why would it connect into the upstream side of the pump on the flow pipe? I think we need better photos and a more extensive pipework diagram (including boiler, feed tanks, etc.) to try to work out what it is.

The valve looks like an isolating valve that has leaked through the spindle, hence the gunge on it. If you scrape that away (it might start leaking!) you should see a slotted circle - which way does the slot point?

Later edit - having looked again at the very poor pic I see that the valved pipe doesn't join the flow pipe under the pump, it just looks like it does. It's as Gasguru said above.

 

[dinger71uk]

so not a good idea to replace it with a straight coupler then. The vlave is fully open at the mo anyway so not really restrictin the flow.

 

[Gasguru]

The cheap and nasty ball valves are restrictive inside so despite it being open it is balancing to some extent, if the radiator system is small you would not notice a system not well balanced.


I noticed that as well Chris, somethings not quite right, more images of further up showing the mid position valve needed.

 

[dinger71uk]

The gunge on it is some compound to stem the flow of water leaking through the screw head on the top side of the valve. The slot on the screw head was in line with pipe. Ill get some more pics in about an hour

 

[chrishutt]

Ill get some more pics in about an hour

Maybe no need if you could just confirm that the pipe coming from that valve does not join the flow pipe leading up to the pump. Your picture makes it look as if it does, but I think it actually runs exactly behind the flow pipe. If so the set-up is as described by Gasguru and you should leave the valve alone if it's not leaking or replace it if it is.

 

[dinger71uk]

Does'nt join the flow pipe to the pump, your right the pipes passes behind the flow pipe. It's leaking quite badly hence the question im grateful for everyones help.

 

[doitall]

For starters the pump is on the normally cylinder return connection or looks like it is anyways.

Would be interesting to see where the common return goes.