Plumbing Related Wonderings!

[Resu]

We recently had an unvented cylinder installed (to replace an old vented one) and the higher pressure of the hot water has made us realise how crap the tap is on the kitchen sink. Had a wee look under the sink and discovered that I have no isolating valve on the hot pipe!

Would I be right in thinking that if I turned off the cold supply to the tank and then run the hot tap the water wouldn't come through?

 

[davesparks]

There should be an isolating valve on the outlet pipe from the new cylinder. You are right that in theory shutting off the inlet will work, but if someone opens another tap then you'll get very wet!

You need to be careful with unvented cylinders, I can't remember the exact circumstances, but I saw one implode when a plumber drained it incorrectly in a hurry. That system had an accumulator tank too so that may have had something to do with it.

I'd suggest reading the manual for the cylinder to check.

 

[Resu]

There should be an isolating valve on the outlet pipe from the new cylinder. You are right that in theory shutting off the inlet will work, but if someone opens another tap then you'll get very wet!

You need to be careful with unvented cylinders, I can't remember the exact circumstances, but I saw one implode when a plumber drained it incorrectly in a hurry. That system had an accumulator tank too so that may have had something to do with it.

I'd suggest reading the manual for the cylinder to check.

There isn't one on the outlet pipe from the cylinder. There is only two valves in the cupboard, one on the cold main which then T's to cold taps, etc. and the other pipe goes to the second isolating valve before the combination valve and then into the tank.

The whole pressurised/imploding thing is what worries me! Someone running another tap is not a worry.

 

[Marvo]

Unvented tanks should have a vacuum valve on both the inlet and outlet side of the tank to stop it from suffering vacuum damage. On old tanks they can get scaled up and occasionally don't open but you say it's new so it shouldn't be a problem.

 

[Resu]

Appreciate the help guys. Not keen on joining a plumbers forum and most plumber mates are out on the town tonight! Excuse the crap photo, Just wanted to double check. Marvo I have these two valves as can be seen, are you saying I should be good to go?

 

[davesparks]

The lever valve should isolate all cold taps and the cold feed to the cylinder
The black lump pointing down is the pressure reducing valve
The black bit sticking up from that is a pressure relief valve, as is the one sticking out of the cylinder with a blue end.

 

[davesparks]

Unvented tanks should have a vacuum valve on both the inlet and outlet side of the tank to stop it from suffering vacuum damage. On old tanks they can get scaled up and occasionally don't open but you say it's new so it shouldn't be a problem.

Presumably that's internal to the cylinder is it?

 

[Marvo]

Usually they're external on cylinders supplied where I live but there's no reason they couldn't be an integral part of the cylinder.

On the diagram below they're at the top and labeled as No5.

 

[Resu]

Usually they're external on cylinders supplied where I live but there's no reason they couldn't be an integral part of the cylinder.

On the diagram below they're at the top and labeled as No5.

View attachment 30191

That's quite common here too although presumably the pressure realise valve 2/3rds the way up mine would do the same thing?

 

[davesparks]

Usually they're external on cylinders supplied where I live but there's no reason they couldn't be an integral part of the cylinder.

On the diagram below they're at the top and labeled as No5.

View attachment 30191

I've never seen one fitted externally to a cylinder yet,