OSO 20 series combi valve location

[slug]

The previous owners of our house had an OSO 20Series 210L hot water tank installed when they fitted a second shower and converted the plumbing to mains pressure.

The plumber installed the combi valve immediately after the stopcock where the water main enters the house instead of at the hot water tank. Looking in the OSO installation manual, I didn't see this listed as a recommended option.

From what I understand, this means that all of the water for the house passes through the combined non return valve/pressure reducer/filter/pressure dump valve. Presumably this limits the flow somewhat and could explain why there is very little pressure on the outside tap?

One other side effect we have noticed is that turning on the cold tap nearest the tank will release hot water initially, I suppose until the pressure, over the mains pressure, in the tank has been released.

On the positive side, I guess this does mean that the pressure on the hot and cold water should always be the same, although since we have thermostatic showers this isn't such a problem.

Is this a valid installation that plumbers use often or should we get it changed?

thanks

slug

 

[chrishutt]

You should get the installation checked by someone who is competent and has the unvented ticket. There may well be other faults if it was put in by someone who was not competent, as appears to be the case.

 

[Agile]

It is quite adequate for a PRV to be fitted at the entry to the property if the pipe sizing is adequate.

However the relevant safety devices should be fitted at the cylinder.

There is usually a filter incorporated in the PRV and these would be cleaned at the annual service by someone certified for unvented cylinders. Its not totally clear to me what your problem is but perhaps that filter is clogged?

Tony

 

[slug]

The only problems we see are the lack of pressure on the outside tap (we haven't got a hosepipe ban yet so the car is still clean) and shower if any other water is being used, and the hot water initially coming out of the cold tap.

Neither of these are critical but a nuisance. Cleaning the filter may improve the flow.

You said that the PRV can be fitted at the entry to the property if the pipe sizing is adequate. There is an additional 8 bar safety device on the tank which I guess passes the other condition.. The house is classified as 5 bedroom (for very small people!) but has a 15mm water main which is then converted to 22mm to go through the combi valve and then back to 15mm for the rest of its travels. On reflection, this probably has a lot to do with the reduced flow.

Thanks for the input

Slug