Poor Flow

[DavePrior]

Apologies if this has been answered elsewhere - I didn;t find it in my searches.

I've just installed a thermostatic shower for a friend, and am inevitably having trouble.
There is very poor flow. They previously had two Mira showers which worked acceptably well, so it's strange that this one doesn't !
Setup is:
Hot water cylinder system, 1st floor en-suite with the hot water tank backing onto the on-suite. Hot water feed from tank, cold water feed from a tank in the loft (previous shower installation instructions specified that this must be the case).
I've put a gauge on the cold water pipe and it didn't register. I've swapped the shower unit for one in another house that I know works well - no change. The shower that I installed at my friend's works fine in the other house.
I've flushed out the pipes, so I'm confident there is no crud in the way. Filters are clear.
My friend doesn't want to to have a pump, but is happy to buy another shower so long as it will work.
I'm considering feeding the cold in from the main rather than the loft tank, will that help at all?
I'm guessing I need:
- suggestions as to thermostatic/mixer showers that work well with low pressure/flow
- suggestions as to how best improve the poor flow

Many thanks in advance!!

 

[Softus]

There is very poor flow. They previously had two Mira showers which worked acceptably well, so it's strange that this one doesn't

Which model did was previously working well, and which make/model have you fitted?

I've put a gauge on the cold water pipe and it didn't register.

Erm, what type of gauge was it?

I'm considering feeding the cold in from the main rather than the loft tank, will that help at all?

That will introduce a new problem, which is that the supplies will be unbalanced. Please don't do that.

...thermostatic/mixer showers that work well with low pressure/flow

How low is the pressure/flow?

How high is the cold storage cistern about the shower handset (the bit with the holes in, not the bit with the controls on)?

suggestions as to how best improve the poor flow

That all depends. You might have an air lock, but we'll know more when you've answered the above questions.

Many thanks in advance!![/quote]

 

[DavePrior]

Thanks Softus.
Don't know the model of Mira shower they had previously, only that it was about 8-10 yrs old. Round mixer, exposed valve, not thermostatic.

Installed shower is a Synergy, catalogue shows that it requires 0.5 bar pressure.

Gauge was from screwfix, suggested on this forum - gauge

Pressure from cold did'nt register on the gauge (I'm answering my ownm question here aren't I)

Cold storage is in loft, so about 6-8ft I would guess, 10ft max above handset when in the rail, 12-14ft above valve.

Assuming the absence of an airlock, (hot tap pressure appears normal apparently), I'm looking for a thermostatic shower that works on low pressure. Any recommendations ?

Thanks again.

 

[Softus]

Pressure from cold did'nt register on the gauge

Cold storage is in loft, so about 6-8ft I would guess, 10ft max above handset when in the rail, 12-14ft above valve.

OK. So if you connected that pressure gauge on a connection at the shower valve, then you'd expect it to read 0.3 bar. Is it sensitive enough for that?

Assuming te absence of an airlock, (hot tap pressure appears normal apparently)...

I think you have entirely independent hot and cold supplies, so functioning hot service doesn't in any way imply lack of an airlock on the cold. Can you measure the flow rate on the cold supply to the valve?

Or are you saying that there is no water there at all? If so, then an isolating valve is shut off, or there's an airlock, or a blockage.

 

[DavePrior]

Hadn't considered an airlock on the cold supply.
Gauge is marked in 0.2 bar gradations, so it's not very clear as to how well 0.3 will register.
It's the cold that I've measured previously - sorry, didn't make that clear.
I haven't measured the hot though.
There is water coming through, but it doesn't give a decent/acceptable shower.

 

[Softus]

Can you measure the flow rate on the cold supply to the valve?

For example, how long does it take to fill a 2 gallon bucket?

 

[plumgas]

How hot is the shower getting, and you said the shower had filters try removing them to see if flow increase and also did you put any of the flow restrictors in instead of a filter

and have you put isolation valves in or gate valves

 

[Bamber gaspipe]

[quote="DavePrior"

Apologies if this has been answered elsewhere - I didn;t find it in my searches.

I've just installed a thermostatic shower for a friend, and am inevitably having trouble.
There is very poor flow. They previously had two Mira showers which worked acceptably well, so it's strange that this one doesn't !

You have installed it incorrectly or fitted the wrong shower.

 

[DavePrior]

Softus - don't know but I'll try to get a measurement soon.

Plumgas - I've had the filters off (they were clean) and no change. There are no flow restrictors fitted that I know of. There is an isolation valve fitted on both hot and cold. Brand new one on the cold, old wheel one on the hot. Not sure I would recognise a gate valve.
Heat from the shower is fine.

Bamber, thanks for that

 

[Softus]

Not sure I would recognise a gate valve.

If you're unlucky, one of these:

And if you're lucky, one of these little beauties:

 

[DavePrior]

Pretty sure there's one of those n the hot (the 1st one I think). If you turn it, it kills the hot water..

 

[DavePrior]

Flow measurements are:
cold water takes 28 seconds to put 8 litres into a bucket
hot water takes over a minute to do the same.
Hot water pressure seems very low.

I'll check the wiki to understand, but to reiterate in case I missed out any detail.
Thermostatic mixer shower instaled to update a working shower. Cold storage tank in loft. The wall on which the shower is mounted backs onto the airing cupboard containing the hot water cylinder. Hot water feed is directly from the pipe that rises from the hot water cylinder. There is an inline isolator on the cold feed to the shower. There is a wheel-type tap like the oe posted by Softus on a separate pipe to the hot water cylinder. Turning this wheel stops the hot water flow.
I'm told that the hot water pressure is normal in the rest of the house.

If I've introduced an airlock, is it simply a case of connect cold to hot and blow it out? How do I know when I've run sufficient cold water in? The washing machine uses hot & cold, so I was planning to connect those two together.

Many thanks for you continued help folks !

 

[Softus]

DavePrior, I'm a bit confused about the cold supply, because I thought you said that there was no flow, but I guess I must have read it wrongly. Anyway, you have a fast cold flow rate, so that's good.

Regarding the hot, could you measure the flow rate from, say, the kitchen hot tap?

Also, seeing as the investigation is likely to head towards the take-off from the hot outlet after the cylinder top connection, please could you describe, and/or post a photo of, this top connection and the shower take-off?

 

[Roadyz]

Flow measurements are:
cold water takes 28 seconds to put 8 litres into a bucket
hot water takes over a minute to do the same.
Hot water pressure seems very low.

I'll check the wiki to understand, but to reiterate in case I missed out any detail.
Thermostatic mixer shower instaled to update a working shower. Cold storage tank in loft. The wall on which the shower is mounted backs onto the airing cupboard containing the hot water cylinder. Hot water feed is directly from the pipe that rises from the hot water cylinder. There is an inline isolator on the cold feed to the shower. There is a wheel-type tap like the oe posted by Softus on a separate pipe to the hot water cylinder. Turning this wheel stops the hot water flow.
I'm told that the hot water pressure is normal in the rest of the house.

If I've introduced an airlock, is it simply a case of connect cold to hot and blow it out? How do I know when I've run sufficient cold water in? The washing machine uses hot & cold, so I was planning to connect those two together.

Many thanks for you continued help folks !

just to make sure the obvious.....

if i understand correctly you have a dedicated hot and cold supply ......... i take it the hot and cold supplys to the shower were the same size?

oh and if it says it needs .5 bar then you shouldnt be fitting it youl prob only get .2.-.3 bar as Pressure = diff in height from cistern to the terminal fitting (shower head) x 9.81

if you fitted the same valve in the downstairs bathroom then all would be good

 

[JohnD]

apart from being shinier, what's the difference between the lucky gatevalve and the unlucky one?