How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Plumberpro Your Own Question
Plumberpro, Plumber
Category: Plumbing
Satisfied Customers: 634
Experience:  Heating and plumbing answers. 20 years experience
Type Your Plumbing Question Here...
Plumberpro is online now

I have a 5 bedroom house, my builder convinced me that I needed

This answer was rated:

I have a 5 bedroom house, my builder convinced me that I needed my gas boiler changed.
He took out my old gas boiler, my copper cylinder, my cold water tank & replaced with a Valliant combi boiler 937 which he said will deal with 2 showers at the same time, I am very upset about the whole performance of my new water system. Is there any remedy apart from a new traditional boiler, copper cylinder, cold water tank system ?
Hi , I am afraid that was the wrong advice . for your size property the advice should have been an unvented cylinder . like a combi this runs off the mains but is capable of much higher flow rates.
If the current system really needs adapting then the best option would be to add an unvented cylinder ( hot water tank) , which would be heated from the current boiler s primary heating circuit .pipe work and controls would need adapting, also the size of the incoming water main would have to be sized correctly. If it wasn't renewed with the building work this may have been why an invented cylinder wasn't put in .
If all this is too much then another so!ution would be to run one of the showers off an electric shower
Customer: replied 2 years ago.

Hello Toby

Thanks for that.

What size unvented cylinder would you recommend for my house, 5 bed

2 bathrooms ? & and what size should the incoming water main be ?

Many thanks


Hi , 210 litre for a cylinder heated by the boiler , 250 litres if heated by immersion heater . The incoming main really should be at least 25 mm ,but the minimum flow rate needed is 20 litres a minute and 1.5 bar pressure. If putting vin a new main is practically impossible , a mains booster set can be fitted , ie in a basement which consists of a tank and pump set.

A mains pipe can be miles moled in as well which is a tunnel under process which can accurately tunnel a mains pipe from the road to a certain part of the house ( just search mains moling)

Customer: replied 2 years ago.

Thanks Toby

Does the 25mm incoming main have to be all the way to the boiler or can it be reduced in the house ?

Hi it can be reduced . normally it would reduce to a 22mm pipe , splitting off to the kitchen and outside tap, before going to the pressure reducing valve ( unvented cylinders are limited to 3 bar for safety ) and then on to cold taps and the cylinder so both supplies are equally balanced
Plumberpro and other Plumbing Specialists are ready to help you