Split coil am wondering?

[DirksPlumbing]

So is this shower valve ok do you think Dirk? A checkvalve on the hot won't or will do the job? Don't apologise, I like as much advice as I can get. At least if it doesn't concern this job, it will be in my mind for others

A check valve on the hot usually prevents the shower pump from operation if it is not a universal head one. Had many crossflowing shower mixers before, causing all sorts of nonsense.

I am not sure what pressure balancing valve you have used and as well what sort of pressures you have on your site. I found some manufacturers only specifying 8bar maximum which we can get close to in some places here at peak times. And I take you have fitted it the right way round (don't think of this being a stupid question, happens to the best too, they just keep it silent). It could point out a malfunction of the valve as well (dirt?).

 

[DirksPlumbing]

The set up is all correct what you say but I have put a pressure balancing shower valve on with the cold mains with a adjustable pressure reducing valve taking it to 1.6 bar, the same as rating as the single impeller hot pump.

Seems doubled up having a PLV and a balancing valve? You could reduce the CWM pressure easily to 1 bar without loosing function as the 1.6 is peak.
Might help it but generally if it is crossflowing it indicates a problem anyway.

 

[mutley racers]

The pressure valve is the right way around and I have put them on the wrong way on occasions. So why does the check valve stop the pump operating? Is that if you put it either side of it? As I know they say not to put one before the pump

 

[DirksPlumbing]

The pressure valve is the right way around and I have put them on the wrong way on occasions. So why does the check valve stop the pump operating? Is that if you put it either side of it? As I know they say not to put one before the pump

One before the pump could cause pressure rise till the pump bursts. Especially in your situation. Positive head pumps have flow sensors. But the check valve does not allow flow to establish as the spring will keep it (near) closed.
For the pump it seems there is no demand and therefore no action.
You sometimes get that to work but often not for long. Once things get a bit stiff by latest it is stopping function.

Universal (negative head) pumps have pressure switches and hold a pressure sufficient to open the check valve. And the other thing they hold is the price tag.

 

[mutley racers]

I have just looked on the salamander site and they have checkvalves fitted on the hot supply from the pump? So it must be ok?

 

[josh]

You mention that the pump is in the loft and if you did put a check valve on the hot up there i don't think there would be sufficient head to make it work, i was always told that a standard impeller pump should be fitted in the airing cupboard (or atleast a floor below the cwsc) to allow there to be enough head for it to make it work.
How come you didn't just drill a cold feed from the cwsc and had a standard twin impeller pump, those pressure equalising valves arn't that cheap are they?

 

[mutley racers]

Well that's it, checkvalve in. And pump running fine. Just need to wait until the morning now for the builder to tell me if it's stopped the overflow or not. To be honest, I don't think it matters where the pump is as long as the shower rose is below it. And mine is a metre below the shower pump and the shower pump is about 100mm below cwsc. To be honest, I was just being lazy rewards to the cold take off from cwsc. I wanted there to be mains in basin for drinking water and thought I will just use that for the shower. The ppressure reducing valve was £20

 

[chris watkins]

You are right mutley pump should work in that position but the reason it is not advisable to have the pump above the shower head, is that it is likely to allow the build up / trapping of air which can damage the pump (cavitation).

 

[DirksPlumbing]

I have just looked on the salamander site and they have checkvalves fitted on the hot supply from the pump? So it must be ok?

Well if you consider "purpose made" and "specified" then yes. It even can help to reduce the mentioned cavitation.

Just I found them (not manufacturers designed ones) getting stuck after a while. Especially if it gets slammed shut by mains pressure.

So you spend quite a bit of money and effort to design a system which has many reasons to fail.

 

[mutley racers]

Well I was out on the driving range this morning hitting a few balls and the builder calls me...well the good news is, it's not coming out of the overflow any more. The bad news is, it's coming out the light fitting above shower. He he. So had to give my balls to someone else and tighten up nut on the service valve.

Thanks for all the help guys. You're all invaluable in my progression as a plumber!!!

I see what you mean by the checkvalve Dirk. When I 1st blew into it it would not budge. Had to give it a good push with my finger. Why did they advise this if this happens to be a problem?