Non return valve suitable for h/w cylindr outlet?

[gerardo]

Hi,

Back home from a 3 day break to see the cylinder header tank outlet pipe dripping at approx 2 drops per second over the front door canopy.
This has happened before and previuosly, I replaced the float valve and attended to the replacement once more. However, thinking that they were leaking, just ran the water off and gave it a clean the second or third time. I cannot remember if I ever confirmed a leak but on reflection I would guess that they have all occurred following days of absence from home.

I was going to toddle off and buy another float valve but did some research here where I noticed a comment on mixer valves leaking cold into the hot, causing the header to overflow and I thought this could be my issue as we now have 4 mixer taps.

I was hoping to fit just one non return valve to the hot tank outlet and wondered if that would work as the leak seems to be quite low (drips)? Does this sound a good idea?

 

[oilboffin]

be careful the coil in the tank hasn't gone that will cause a leak back

 

[doitall]

Anything stopping the flow on the cylinder could cause it to explode or implode depending where you put it.

Dangerous to say the least.

 

[gerardo]

Thanks for the replies.

I was intending to put the valve on the hot water outlet, therefore only needing 1 rather than each of the taps. Is that okay?

How can I tell if the coils has gone? Would there be CH inhibitor leaking into the hot supply from the radiator side of the system?

 

[doitall]

No it is not all right.

To check the coils is gone one or the other tanks in the roof must be higher water level than the other and the ball valve running in the highest.

If the boiler is a sealed sytem, is the gauge dropping to zero.

Must likely problem going on your opening post is the ballvalve needs replacing.

 

[Onetap]

I was hoping to fit just one non return valve to the hot tank outlet and wondered if that would work as the leak seems to be quite low (drips)? Does this sound a good idea?

Not really. The hot water outlet connects to the open vent. The open vent is the escape route for steam, in the event that the immersion heater sticks on, as they do. There's no pressure relief valve. There shouldn't be any valves at all between the that outlet and the open vent discharge, not even an NRV that shouldn't obstruct the steam if it works as intended.

I'd just find the leak.

 

[gerardo]

Again, thanks.

The boiler is a system boiler and the issue started before fitting the new pressurised one.

Please forgive my naivety, I thought that the hot water tank had one outlet feeding all hot taps and therefore fitting one at the outlet would protect all of them rather than one per tap. Would finding the outlet furthest from the junction to the hot water feed suffice?

I assume I am correctly referring to a one way valve as fitted to hot taps?

As you can guess I am not a plumber, but keen to understand what may be the issue/resolution. As I have replaced the valve with a new platsic flow master (I think) I thought that 3 times for this to happen and whilst on leave is slightly more than a coincidence.

Again, thanks for the advice.

 

[doitall]

Ok so you now have a sealed system boiler with a filler loop.

That rules out the coil unless the boiler is loosing pressure, or, the filler is letting by. Both unlikely at the same time.

You went away for a few days and the tank was starting to drip, that suggests the ballvalve is not shutting off and the storage tank is slowly filling up.

When in use it doesn't happen because you are using hot water and lowering the level.

 

[gerardo]

Hi doitall,

To clarify, the boiler is a Remeha Avanta 24S system boiler with a header tank for the immersion tank in a bedroom.

I have not noticed any issues regarding this other than explained, even with the old boiler with the extra header in the loft.

I really do think that I have only noticed the problem since coming back fro leave in 2008 when the old boiler was still here.

I changed the old flow ball valve to a new plastic type without the ball but it is quite noisy. I noticed the oerflow dripping and bought another as well as spare seals but just replaced it rather than the seal IIRC.

Back from a few days away and still leaking but ran the hot tap to drop the level so not looked to se if it is dripping. Read this site and came up with the evidence that it may be back pressure via the mixers, hence fitting an a back flow preventing valve at the hot water outlet.

I hope this makes sense?

 

[doitall]

Yes makes sense, but if you are not using any water, e.g. open any taps you shouldn't get a backfeed.

I would put a brass ballvalve and float back in the storage tank.

To get a backflow, the hot and cold must be different pressured, Mains cold/ tank hot for example, then when you open the outlet the cold goes back up the hot pipe, best place to look is the kitchen sink first, run the hot then when you open the cold does the hot pipe go cold.

If the above is happening and the high pressure is going into the cylinder it needs to get out or burst.

Incidentally if, you were getting a backfeed the storage tank would get hot, I think you would have mentioned that if it was.

 

[gerardo]

Thanks, will try again with a new float valve.
I was going to do this but read that a poster noted a leaking mixer causing a back flow issue as I had when not in use (like me being away).
It's been a while.. What type of seal do I need between the nut from the outlet pipe and the thread for he valve please?

 

[doitall]

What type of seal do I need between the nut from the outlet pipe and the thread for he valve please?

Explain.

Assuming you mean where the ballvalve connects to the mains, then a fibre washer should be all you need.

For information, a back feed when the outlets are turned off is very rare.

 

[gerardo]

Sorry, when I fit the new valve, what seal does it need.. Not sure if it has an olive, washer etc!

 

[doitall]

See my edit, a fibre washer usually.