plumbers of ocuk... crazy airing cupboard & shower issue...

[spearchew]

Hi there,
I'd be very grateful for a second opinion on the following issue...

(1) My shower is *very* unreliable and seemingly getting worse. The cold water flow is good and reliable, but when I turn the mixer valve to hot, the flow will often reduce to a trickle. The "trick" to getting it working is to slowly turn the valve from cold to hot.
(2) There is very strong evidence that the shower is pulling in air and I think this must be the root of the problem. As I turn the shower from cold to hot, the valve will vibrate a bit and create a knocking sound, as though air is being forced through.
(3) Sadly, there seems to be an unlimited supply of air getting in. I'm quite sure there are no water leaks (based on my experiences with this house, I believe I would be able to hear a running water leak).
(4) the pressure gauge next to the filling loop in my airing cupboard consistently shows 1 bar.

I wonder if anyone has any thoughts as to what is going wrong here and what the solution might be? I bought this old house (90 yrs old) quite recently and am still learning about its issues...

Many thanks indeed for any help,

 

[robj20]

Depending exactly how your system is setup. But where your pump gets the hot water from the tank, the pipe above then splits, is the thicker pipe a breather/overflow pipe, ie goes up to the cold water tank and just feeds into it but above water level. If so, you could well be pulling air in that way I guess if the pump is strong enough.

If that's the case a simple way around that is to fit a one way valve so if the tank gets too hot the water can still escape but when your pump tries to pull water and air that way it can't and can only pull water from the tank.

 

[Danm54]

If that's the case a simple way around that is to fit a one way valve so if the tank gets too hot the water can still escape but when your pump tries to pull water and air that way it can't and can only pull water from the tank.

Yea, dont do that. There shouldn't be any valve or restriction in the expansion pipe, it's there and open for a very good reason.

You could check that the height of the expansion pipe is correct though, quite often they're fitted just over the top of the tank when they really need to be 300-400mm over the water level.
There is a calculation for it but I'd always fit them as high as possible within reason. Depends how much height you have above the tank.

Other than that it looks to be installed ok, make sure the gate valve feeding the pump is open all the way as well.

 

[spearchew]

Thanks for the info guys.
Not sure if these additional pics are in any way helpful to diagnosing the issue but it may be interesting to note the additional connection to the aqualisa shower pump...

 

[Django x2]

Your pump should ideally be above the shower. It's been put where it is because of sheer lazyness

 

[spearchew]

thanks for your input everyone,
I'm currently feeling a bit fed-up with how over-engineered the heating / shower system in my house seems to be.
I've just posted a "job spec" to mybuilder.com for removal of the cylinder and installation of a pressurised cylinder + removal of shower pumps.
Obviously I'm no expert but perhaps this is would be a worthwhile "reset".

edit: my flow rate from cold mains is below 10l/minute. internet says i need 20lt at minimum... so that's a dead idea then

 

[The Artfull Bodger]

Isolate water supply to shower, turn off pump, remove shower and check filters, open water supply slightly and flush through with pump off. Do you by any chance have old iron pipework in your system?
Edit: assuming the model is acute. Check green flow restrictor is used on cold side and yellow is used on hot side.

 

[The Artfull Bodger]

edit: my flow rate from cold mains is below 10l/minute. internet says i need 20lt at minimum... so that's a dead idea then

Hardly anyone has 20l/minute on mains, your using a pump from a cistern in your roof so shouldn't make a difference as long as your tank is large enough.
Edit: so just reread, don't need 20l min for unvented cylinder trust me, get someone round to check it if your that keen, they can advise you always check flow rate on something like an outside tap, worst case an accumulator would be needed.

 

[Tachyon]

Your pump should ideally be above the shower. It's been put where it is because of sheer lazyness

Interested in why you say this. I'm not a plumber but enjoy DIY and thought the lower the pump the better the pressure head it would be getting?

 

[Danm54]

Your pump should ideally be above the shower. It's been put where it is because of sheer lazyness

No it shouldn't, the pump should be exactly where it is.

If you put the pump higher than the top of the cylinder then you run the risk of getting air locks in the supply pipework.
It can be fitted higher, but in most cases you can't fit it in the loft and still get the required head from the cold water tank.
Every pump I remember fitting had the best location at the base of the cylinder.
It's also generally more work to fit a pump there as well so it's not sheer lazyness either.

 

[Peerzy]

We're having our en-suite done at the moment and spoke with the plumber (who is excellent) about the location of the pump. Near the cylinder was his recommendation as the best, but due to noise being near bedrooms this wasn't suitable. He's said we can get a certain type of pump (negative head from memory) that is slightly more expensive to go in the loft which is what we've gone for.

 

[theone8181]

While I cant offer any advice, that is some crazy plumbing. How does anyone know where the pipes run when they are going through the floor.

 

[ChroniC]

Not a plumber, but I was always under the assumption that the noise you describe is called water hammer.

A water hammer occurs when a water valve is suddenly shut off. All the water that was running then crashes into the valve, shaking your pipes, creating the knocking noise you hear. .

Would this not suggest that your mixer is busted and causing problems for your water pump, which would be why your getting a crap trickle when you turn it to hot?

Obviously this is a total guess, like I said, not a plumber.

 

[Django x2]

Interested in why you say this. I'm not a plumber but enjoy DIY and thought the lower the pump the better the pressure head it would be getting?

No it shouldn't, the pump should be exactly where it is.

If you put the pump higher than the top of the cylinder then you run the risk of getting air locks in the supply pipework.
It can be fitted higher, but in most cases you can't fit it in the loft and still get the required head from the cold water tank.
Every pump I remember fitting had the best location at the base of the cylinder.
It's also generally more work to fit a pump there as well so it's not sheer lazyness either.

Sorry yes you guys are right, I had it in my head a previous install I did where the cylinder was in the loft too, but yes, pump should be lower than cylinder.

 

[Ronty]

The gate valve on the hot inlet to your pump could be partially closed. They have a tendancy to not open properly once closed, and if your shower valve is only 6 months old the I imagine it's been shut of recently.

 

[mickyflinn]

Get british gas back and say theres something wrong with the shower there will have a quick look and probablly point you in the right direction.