Posting a message to the forum will remove the above advertisement
  1. Checkout our Plumbers Insurance area - heavily discounted Public Liability Insurance and Van Insurance specifically designed for plumbers.

Discuss Legal pump on mains? in the Water Regulations area at

Thread Status:
Not open for further replies.
  1. TimT

    TimT Guest

    I live in a block of flats. We have excellent (turn the taps on and stand back excellent!) cold mains direct into each property, no tanks in lofts etc. The hot is supplied via a copper immersion cylinder in each flat - the pressure being from a small header tank atop the hot tank. Hot pressure is next to useless, in fact, it is useless.

    My neighbour has just had a pump fitted in his flat to boost the hot, and to achieve this had a regulator fitted to the cold mains inlet which I presume lowers the pressure at which it enters the pump. The pump is connected to both hot and cold supplies to his taps/shower.

    My neighbour now has excellent pressure on his hot water, and cold.

    I had quotes to fit hot water systems in my flat (unvented, pressured I think?) and the cost ran to £1500 to £1800. I was then thinking of going for a thermal storage solution as it is apparently a better system, and the cost went over £2000

    My neighbour got his pump done at mates rates circa £200.

    I was told I could not have a pump fitted by a plumber who quoted me for the works above. Not allowed, illegal or similar words were used.

    Facts please? I can't find the definitive answer on Google, only something about pumps which boost the supply of cold. I just want to increase the pressue of my hot water so I can take a reasonably pleasant shower instead of doing piroettes under a drip every morning.

  2. Spanner2k7

    Spanner2k7 Plumber GSR

    As I understand you can only fit a pump to the mains is the pump does not exceed a flow rate of 12 litres per minute. Sounds like you have a combination cylinder, and I would be guessing that your neighbour has put a pump on the hot to increase its pressure. Then reduced the mains pressure at mains to achieve balanced pressures.
    The problem with that is if you draw to much hot water quickly you will run out as the cold feed can supply a certain amount via the ball valve.
    • Like Like x 2
  3. Howsie

    Howsie Plumber

    You should be able to pump the hot from the cylinder and the cold from the CWSC that feeds the cylinder. This is the right way to do it.
  4. Ray Stafford

    Ray Stafford Guest

    I think its a Fortic Howsie from the description in the OP. No CWSC.


    Coming back to the core problem, if your neighbour has the same system as you, then he has problems coming down the line - particularly if he runs the hot for any length of time. Eventually the pump will be sucking air, which will significantly reduce its life.

    It is legal to pump the cold main, up to 12 litres per min. It had used to be illegal, and some older tradesmen may not be up to date with current regs. However, I don't think this is the issue here.

    It is legal to pump a fortic tank (which is what I think you are describing - a cylinder with a little header tank built into the top?) Legal, but foolish. The header tank doesn't contain enough water, and it won't fill via the ballvalve anywhere near fast enough to replenish what the pump is drawing, so eventually the pump will suck fresh air. Goodnight pump.

    It sounds to me like your neighbour has bodged something together which will work ok for short bursts, but is not a long term solution.

    If, as you say, you have plenty of flow and pressure on the incoming main, you should be able to benefit from an unvented hot water cylinder, giving you plenty of high pressure hot water. This needs to be fitted by a G3 qualified installer, but unless you insist on rolls-royce branded product, shouldn't cost £1800. Although without seeing it, its hard to be sure.
    • Like Like x 2
  5. Howsie

    Howsie Plumber

    Well spotted Ray! You should think about getting into this game for a living! ;)
    • Like Like x 1
Similar Threads - Legal pump mains Forum Date
I thought you couldn't pump mains legally? Plumbers Arms Dec 17, 2017
1 Rad only working with pump on full Central Heating Forum Jan 6, 2018
Thread Status:
Not open for further replies.