DIY Doctor UK DIY Forums

Hi all,

I'm refitting and re-tiling our en-suite, got as far as plumbing in the new thermo mixer shower but I can't get decent pressure when I lift it above head height. It turns to a dribble.

Its an open vented heating system, hot water is piped upwards to valve and the cold water comes downwards from tank into valve.

The old shower worked fine and was a similar thermo concealed mixer.

Heres a photo (hopefully it works)


Is the low pressure simply because there are too many elbows?
I didn't want the bulkhead directly above the valve controls as the shower cord would overhang them.
I had the fit loads of PFTE to the hot/cold inlet elbows on the valve to get them pointing in right direction securely, is this safe or prone to leaks?

Any tips appreciated, thanks. :?

Heres a link to the shower if it helps

Google "plumbworld.co.uk/triton-alcor-dual-control-2767-20362?CAWELAID=408198304&ctype=2&gclid=CPqRnIeqjaYCFQkf4QodUhXUog"

PNEFC wrote:Is the low pressure simply because there are too many elbows?

No, unlikely.

Most likely the new mixer shower is not able to work with such a low pressure system.

All modern showers now have to be able to work when fitted to mains pressure systems which means there is a trade off against efficiency when working with very low pressure systems.

For even the best showers the minimum head will be about 1 metre which means the header tanks must be on legs in the loft. Any lower will not do.

The solution might require a pump to be fitted.

Check the specification of the shower to ensure it is designed to work at 0.1 bar.

PNEFC,
You just haven't got sufficient head of water for this shower to work. You need at least 1m from the head in its highest position to the water level in the tank. Either fit a pump or raise the cold water tank on a platform.
end

stoneyboy wrote:PNEFC,
You just haven't got sufficient head of water for this shower to work. You need at least 1m from the head in its highest position to the water level in the tank. Either fit a pump or raise the cold water tank on a platform.
end

Thanks for the replies chaps,

I've checked and the tank in the loft is already raised by over a metre.
I think there is probably at least 1.3m head.

I've also checked the spec of the shower which states
SITE REQUIREMENTS
The installation must be in accordance with
Water Regulations and Byelaws.
Running water pressure:
Gravity fed – 0.1 bar min.
1.0 bar max.
Mains fed – 1.0 bar min.
5.0 bar max.

Maximum static water pressure:
Gravity and mains – 10 bar

Shower spray is fine when I lower the head to waist height.
Was hoping to avoid fitting a pump as don't have much room under shower tray or in dry wall.

Any more suggestions appreciated.
thanks

PNEFC wrote:Shower spray is fine when I lower the head to waist height.
Was hoping to avoid fitting a pump as don't have much room under shower tray or in dry wall.

Any more suggestions appreciated.
thanks

Sometimes shower valves are fitted with non return valves and these can reduce the flow.

I can't actually tell the diameter from the photo, but the pipe from the valve to the outlet is rather longer than normal and if it is only 15mm that may reduce the flow.

Unless the shower is unusually far away from the header tank, I can't imagine what else could be wrong other than the manufacturer has been "optimistic" about their shower performance.

You haven't fitted any flow restricting fittings in either the feeds or outlet pipe?

Thanks for reply plumbbob,

It is 15mm pipe from the valve, and I haven't fitted any flow restrictors and can't see any along the visible pipework.

I think I'll try and reposition the bulkhead closer to the valve with fewer elbows as the push fit ones I got seem narrower than 15mm in the middle.

If I got some 15mm to 22mm couplers and used 22mm pipe between valve and bulkhead would that help?

Failing that I may go for a power shower but I'm not clear on how to measure the empty rate of my cold tank and whether it will be sufficient?

PNEFC wrote:If I got some 15mm to 22mm couplers and used 22mm pipe between valve and bulkhead would that help?

It is always a good idea to use 22mm for the outlet on low pressure showers. I won't guarantee it curing your problem though, because I can't see why the flow is so poor now anyway.

One thing I have just noticed, the hot supply on the left comes up from below. Where's that from then?? Have you taken it from the bath tap or something instead of its own feed from the hot water cylinder? Also, it's going to be a bit of a challenge retro fitting a pump if the feeds come from different directions.

PNEFC wrote:Failing that I may go for a power shower but I'm not clear on how to measure the empty rate of my cold tank and whether it will be sufficient?

Generally, a power shower will work from a standard header tank unless the incoming mains is poor or the hot water cylinder is smaller than standard. Suck it and see.

PNEFC wrote:I had the fit loads of PFTE to the hot/cold inlet elbows on the valve to get them pointing in right direction securely, is this safe or prone to leaks?

I know, damn nightmare they are. Even with 15 turns of PTFE they still leak! I avoid using elbows for of this reason. Leave it under pressure overnight then check the joints for any moistness the next day. Be vigilant.

plumbbob wrote:One thing I have just noticed, the hot supply on the left comes up from below. Where's that from then?? Have you taken it from the bath tap or something instead of its own feed from the hot water cylinder? Also, it's going to be a bit of a challenge retro fitting a pump if the feeds come from different directions.
.

I haven't traced it but I assume the hot supply comes straight from the cylinder as the cylinder is across the landing and is closer to the en-suite than the bathroom.

I'll give it a try with some 22mm couplers/pipe and fewer elbows etc.
I'm swaying towards an electric one now, I'd have to get a sparky out for a power shower anyway and I think I can tee off the cold mains feed into the tank in attic relatively easily. So an electric one would work out cheaper and they seem a bit more reliable than power showers.

Thanks for your help :)

Of course, the final decision is yours, but it seems such a shame when you are so close to a result but then choose to go in the direction of an inferior product.

Electric showers will never perform as well as a mixer shower, and certainly not a patch on a power shower.

The cost of installing a 10mm cable won't be cheap either and there might be other issues with the consumer unit. A pump only uses a couple of amps so if there was a socket nearby, you could even do the electrical side yourself. (Plug pump into socket.)

I wouldn't say power showers are any less reliable than any other equipment. For example, I fitted mine over 20 years ago and although I changed the shower valve when I refitted the bathroom, the pump is original and it is still used daily by a family of four.

Still struggling with this.
I'm swaying away from electric now as I'm not sure the mains pressure is any better and due to the likely cost of the wiring.

So I think I need a pump or power shower.

I have a 36 gallon hot cylinder and the cold tank is 25 gallon I think. It also has a smaller tank along side it which I presume is for the central heating, the 2 don't appear to be linked. The central heating has a pump fitted in the airing cupboard next to the cylinder.

The feed from the 25G cold tank supplies the bathroom first and then the ensuite where I'm fitting the shower.
As there is only one 15mm output from the cylinder so I presume there is no dedicated hot water shower feed. (All under floorboards so can't tell).

I'm not sure whether the 25G tank and the fact that the supply pipes feed other outlets will be suitable for a power shower??? Will it draw in air when any other taps are opened?

I haven't got room in the vicinity of the shower for a dedicated shower pump due to partition walls and only a 100mm space under the shower tray. If I get a negative head one in the attic I'm not sure the hot feed will get up that far?

Is it possible to fit a pump in the airing cupboard for the hot water supply to all outlets? And then a seperate one near the cold tank to get equal pressure?

Think I'm getting out of my depth so will probably get a plumber in for a quote, but any tips for me (and others) would be great - thanks.