Plumbing: shower room and bathroom - insufficient water pressure?

You are not alone on this and this is a very common shortcoming of so many plumbers, supposed gas installers, and more often the building contractor.

A little more information would be nice on the make and model, however any good engineer would never EVER fit a combi to run two showers simultaneous as they just simply cant give out the hot water unless the water pressure is very good, the boiler can cope, and the shower will work in tandem with another. The only time i have ever fitted a combi to a twin shower (thermostatic) domestic system is when i have got it in writing the customer definately wants a combi as opposed to an unvented (often referred to as a megaflow) system or a tank and open vented system with gravity or pump assisted system.

Also if they fitted a shower and it is not thermostatic they risk burning you but that is by the by, but helps weight in civil court.

I would put money on that they fitted you a cheap barstyle shower with a 24-28kw combi boiler - if it is a ferolli, ideal, vokera, biasi, glowworm then they are penny pinching. A lot of contractors tell the plumber what to fit, push for payment and then hope your complaints go away before the dust settles and you notice the faults.

Rectification info:

Where your boiler is situated - can they fit even a small cylinder i.e 500mm diameter wide by 900mm high? If so then you can fit an unvented cylinder (not requiring tanks) which will greatly improve your situation for less than £2k (guess - without seeing your property) or even for free as they have cocked up royal. Your newly fitted combi can be used - it will just be effectively a Sytem boiler on an S-Plan (google it - i often use existing combi boilers this way and its perfectly safe and legal and good practice) with the added bonus of an immersion heater incase of boiler failure.

Withhold not all, but the amount it will cost to rectify - however you must be CERTAIN you gave no indication that you wanted a combi.

The best example of a combi being able to run 2 showers simultaneously is a Worcester Greenstar 30Si running off a 25mm blue alkethene cold main and then 22mm pipe to the boiler (within 1 meter)then splitting down to 15mm 3 ways to the boiler, shower (1) and shower (2) before ANYTHING else. The house was a very big detached bungalow and was a unique layout. The showers were Mira Codas and it worked magnificent. Anything less, and without specific written request by the client/customer, fit an unvented cylinder or simply dont - do - the job! Its not worth the comeback.

Dont forget your contractor, or gas fitter (is he qualified? If not you will breeze it in court - ask for your boiler registration document from GasSafe) is looking to make a profit, and any monkey can spanner in a combi. Its not hard. However some take the p.155 and get greedy on their profit margin. More often than not - they havent a clue how to fit anything else but combis!

Give them the chance to explain their side with all effected parties present after seeking other sources of information like other gas fitters (but remember - we all know each other at the merchants so be nice about it so as not to blow your gameplan) and give them a chance to rectify. If the bill wasnt unreasonable, or even good - say you will buy the cylinder (anything from £300 to £800 pending capacity) and they fit for free or you withhold part payment (i.e labour of rectification as the boiler is still good providing its legal - if not withhold the lot!)

Would like to have more info but think this will help you and good luck - this is very common and you are not the first and wont be the last!

P.S if you are in England dont be mislead into being told you can fit pumps - you try fitting a pump to your cold main and it will blow itself to bits. Yes you can buy cold water main booster pumps but they are a poor and desperate measure making little difference and costing upwards of £300 trade and will make NO DIFFERENCE TO THE COMBIS HOT WATER OUTPUT. None.

Plus its another £300+ to fork out every time it breaks.

You cant beat good install. Dont try and patch.

I would withhold between a third and half of the plumbing bill until they resolve the problem, but you should write to them with recorded post and say that you are doing so, and why.

Taking out your existing water tank was a mistake because this caused your water pressure to fall.

The line pressure is obviously not adequate for two bathrooms and all the other sanitation.

They are the experts and should have been aware of this !

You didn't need to specify that both showers might function simultaneously because that is stating the obvious. You don't need to tell an electrician that all the lights could be turned on at the same time, without blowing all the fuses, which is pretty much the same.

It must be possible to install a pump which would increase the inlet pressure without needing a tank, perhaps you could ask the plumbing company if this is possible.

It is also possible that the Combi unit they installed is not man enough for your requirements, and if this needs to be updated to a better model, the plumber should normally pay most of the cost of this.

You could offer to pay the difference in the costs of the two models in order to avoid a long and costly dispute, and even some of the labour costs.

In any event, expect to pay something towards solving this problem.

Obviously there was a breakdown in communication and both you and the plumber made some mistakes. It is far better to come to a mutual agreement than have this matter come before a court. Because then you both lose in the end.

Do not go to another plumber, because unless you give the existing one a chance to solve the problem, you cannot deduct someone else's work costs from their bill.

In a court of law you will be forced to pay the rest.

I wish you luck ......

If the combi was a large one the flow would probably have been adequate. Large combis cost a bit more but have a high water flow rating. They don't cost any more to run as the flame modulates. All this assumes your mains pressure is reasonable. Something else to ascertain.

im a builder uk ..but build in europe ..have a home in south of france ...there the water pressure is low ..as it is in all the area ..so all builders merchants sell water pumps ..i have one fitted ..in line on the mains ..the difference is chalk and cheese ..this is one option for you ...but you mention a tank and pump ...DO NOT install a tank fed shower ..only mains fed will keep you safe ..if you go away and come back the water could have been in tank for many weeks ...not good ..your rising main is your only pressure unless you install a pressure vessel ..ask your plumber ..

consult a solicitor, but if it helps we only have 1 shower, you cant use it when the washing machine is on.