low pressure on shower!!!

[dan_the_plumber]

Hello all

I have a problem with a new shower installed in that there is low pressure on the cold supply

There has always been a problem with the cold supply pressure but apparently it used to be ok and it's got gradually worse over time even with the old shower in place.

customer went out and bought a new shower which i fitted

Apparently the pressure is ok when shower first turned on and then the pessure drops out almost completely

As far as i can tell the shower has a seperate feed from the storage cistern in the attic (I could not isolate from cold main)

The shower head is quite high (400mm from ceiling)

I should imagine the amount of head is not more than a meter from the rose to the level of the water in storage cistern.

I was wondering the best solution to the problem.

I haven't had chance to get up in the attic to have a look yet but i wanted to go to job loaded with as much information as can get

Ideas I've had are:

1. To raise the cistern up by building a trellace and resting the cistern on top
2. To disconnect the feed to the shower from the cistern and then tee off the cold supply to the cistern (at mains pressure) and connect into shower
3. Could be a mall functioning ball valve (sticking closed and resricting the flow into the cistern
4. Some kind of blockage on the supply pipe to the shower maybe some insulation or sediment in cistern.
5. Malfunctioning gate valve on the shower supply pipe
6. customer thinks it may be due to air lock

I wonder if anyone could suggest what the most likely cause would be? Which may not be any of the ones i've thought of

The thing thats confusing me is that it's coming through fine and then after a few mins it's not?

Thanks very much....Dan

 

[ecowarm]

Where is the hot supply from? the same tank?

 

[dan_the_plumber]

The hot tank is in the airing cupboard right down the other end of the large house

I am not sure as yet whether cold is fed off same cistern as supplies the hot tank

It's such a large house maybe it makes sense to supply the shower off a completely seperate cistern

I've not had chance to look in attic yet

Thanks for any advice

Regards...Dan

 

[ecowarm]

If fed from a different tank there could be issues with different head to hot/ cold. You could try back feeding from a mains water tap to blow any air/ blockage out. Ideally get up in the loft and investigate the pipework.

 

[dan_the_plumber]

Ok thats good idvice thanks

One thing just to be clear....By back feeding from the main, do you mean disconnecting from the cistern and teeing into the main supply which currently supplies the CWSC?

Thanks a lot

 

[dan_the_plumber]

Oh yeah and one other thing....Sorry

It's a thermostatic mixer shower.

If cold is fed from mains and hot is fed from storage it may result in unequal pressures

Dya think that'll be ok?

Thanks

 

[dancinplumba]

not good idea, pressure needs to be equal, you could try pressure equalising valve ?
imo

 

[heliotrope]

You say it is a thermostatic mixer shower.

Did you (or the custmer) check that it is suitable
for use from a low pressure supply?

 

[dan_the_plumber]

Yeah it says it is suitable for all plumbing systems and unequal pressures

Just interested what others have to say on the subject

Because as I am learning things are not always exactly how manifacturers say

 

[dancinplumba]

whe shr turned on does just cold shut off? or does hot shut off as well ?

 

[dan_the_plumber]

They both shut off
And the shower just goes to a drip

 

[dancinplumba]

wot happens if you put shr head really low ?

 

[dan_the_plumber]

Agh good thinking but it's a rigid shower design

 

[dancinplumba]

if you could somehow do it and it worked them you know its pressure issue,
its new shr maybe its faulty ?

 

[dan_the_plumber]

Yeah sure.....I am pretty sure it's a pressure issue and not the shower.

I actually had to fit the shower live. I couldn't isolate the cold! The hot was ok coz i could isolate the gate valve above cylinder

I guess the cold gate valve is in the attick and with the high ceilings and a short ladder i didn't fancy the climb

So anyway I did actually see that the cold is pretty low pressure but hoped it would be enough

Dough!.....Should have used a pressure guage or flow cup on the supply pipe first but a very exited customer rushed out to buy a shower before i had chance

 

[TerryH]

Is it correctthat there is good pressure initially before it reduces to a trickle?
I had this some months ago but the fault was on the hot side, irregular and difficult to duplicate, fine for weeks and then it played up again before returning to a well behaved shower.
I climbed up to the cwsc and fiddled about with the hw cold feed which had a redundant non-working valve just outside the cwsc.
I felt about with my finger to see if there was a block.... there was. I used a piece of bent hangar wire and hooked out a disc cut by a hole cutter and left in the tank by the installer. My guess is that it had been sucked up when I was putting in my cold feed on the opposite side of the tank.
So.... to cut a long story short, check the cold feed, maybe even just cut to the chase and put a new one in.
TerryH

 

[j0hnb0y]

hello gents , id bet a £10er its just an air lock !!

 

[dan_the_plumber]

Yeah all good suggestions about the cold feed....Thanks for that I will certainly bare that in mind when I'm up the floft hopping between joinsts

As for your £10 on an airlock, your money might well be safe my friend!

Apparently 3 plumbers came before me and at least 2 ended up with an air lock....So says customer.

Not really sure what to do about it though....I might cut an auto air vent in above the shower or something!?

 

[dancinplumba]

shove wet vac on shr outlet?

 

[dan_the_plumber]

hello gents , id bet a £10er its just an air lock !!

Sorry mate I meant to get back to you.

You were dead right it was just an air lock

I guess your money was the smart money

Cheers...Dan