Plumbing Question

Very high pressure from hot bath tap but poor shower pressure from same pipe

If anyone likes a puzzle, read this!

I've recently had a mixer shower fitted over my bath. It's not electric. I have a gravity system, not a combi-boiler. The house was built in 2007 and originally had a mixer tap on the bath with a shower head with the push down collar type of switch to alter the water flow from the taps to the shower head.

When I collected the keys, I was told something was done differently when plumbing the bathroom so when using the shower bit, I'd have to turn the hot on first, then gradually add cold in until I got the required mix.

The collar never worked properly so I had the mixer tap replaced with separate hot and cold taps and both have very good pressure; higher than the rest of the house, and the hot is even a bit higher than the cold.

Now I've had a shower fitted over the bath and was told that based on such good pressure, I probably wouldn't need a pump. The shower is just about good enough to wash under but nowhere near as good as the taps, and the plumber has T'd into the same pipes that feed the bath taps. We're both stumped as to why it's so rubbish!

I have an en-suite shower and basin, the main bathroom basin, a kitchen sink with mixer, all which have considerably less pressure than the bath. There is a downstairs basin almost directly under the bath, and the pressure on these seem high too, although maybe slightly less than the bath.

Sorry for the lengthy description but we've already checked some things and don't want to go over old ground if possible. Does anyone have any ideas which might help get decent (but not waterfall!) pressure from the shower without a pump?

4 Answers

Best Answer

Don't get flow and pressure mixed up. You will have good flow of hot to the bath because it its Fed by 22mm pipe, and the tap will have a larger bore. A mixer shower has to be fed with 15mm pipe(it helps if 22mm is ran as close as poss to the shower) but the bore through the shower and hose is small. Therefore without high pressure the water flow is reduced. The only real answer is to install a pump.

Answered 10th Feb 2015

Fixed Price Plumbing

Member since 9 Feb 2015

If your hot water cylinder is on the same floor as your bathroom, expect poor flow rate to mixer shower only. Best way to cure this is convert mixer shower to a power shower by simply having a plumber fit a good quality shower booster pump such as Stuart & Turner or Grundfos, make sure he fits the right type of pump i.e. negative head or positive head!

Answered 20th Feb 2014

Boiler Homecare

Member since 6 Jan 2010

Get a proper plumber to look at the problem, one that understands about head pressure and equal pressures between hot/cold because it sounds like the plumber you are using at the moment is to use your words stumped, which for you makes him as much use as a chocolate tea pot.

Answered 22nd Feb 2014

kevin cassidy building contractors

Member since 16 Dec 2010

It sounds to me as if the cold to your bath may well be fed from the mains which perfectly explains why you were told what you were about the tap when you picked up the keys. I would suggest that originally the bath taps were separate pillar taps & later changed for a BSM. Either that or the BSM was illegal when first fitted.
Either way, when your shower was fitted the type of supply to the cold feed pipe should have been checked.
Another thought is that depending on the shower valve, it may be fitted with flow restrictors as standard. It is quite a common practice these days & if it is marked up on the box as a water saving product then it's almost certain they will be fitted. If it is a low pressure supply then this could also explain it. Don't confuse pressure with flow rate, if it is tank fed then it will be a LP supply, unless of course the tank is extremely high up. The higher the head the greater the pressure. 1 atmosphere for every metre. If the tank is just above the ceiling joists then you will have barely 1/2 a metre above the shower head but around 2 at the tap outlet. If this is the case the you can either raise the tank or look into fitting a pump, the latter meaning re-plumbing.
Also, depending on the property, it would usually be far better & less messy to supply the shower separately from above. Your plumber (& I use the term loosley), didn't know what he was doing. Get someone who does for a proper opinion.

Answered 13th Nov 2016

Martin House Plumbing Services

Member since 27 Apr 2016

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