Cold tank raised, water pressure lowered!?

Discussion in 'Plumbers' Talk' started by Tom J, Feb 15, 2020.

  1. Tom J

    Tom J New Member

    The Bathroom (Upstairs) has such poor water pressure that the taps are no better than a trickle. The bath and basin have had their filters removed to try increase the flow.

    The cold water tank in our loft was around 4" off the floor. We have now raised it to the highest point practically. With the rise, I had to use 135° couplings for the extension to the copper pipes (22mm).

    The water pressure has since dropped and I have checked all of the filters in the outlets with no blockages.

    Any ideas as I'm stumped...
     
  2. DIY0001

    DIY0001 Active Member

    Are the bathroom cold taps actually coming from the cold water tank rather than the mains? Usually at least the basin is mains fed for hygienic reasons.
     
  3. Tom J

    Tom J New Member

    More than likely as the pipes come up from the floor to the bathroom. However the pressure drops drastically as the kitchen sink is adequate.
     
  4. DIY0001

    DIY0001 Active Member

    Pipes for basin and bath usually do come up from the floor. It isn't an indication of whether the supply is mains or gravity from tank. Turn the mains off at the stop-cock, usually under the kitchen sink, and check if the basin and the bath taps still run water.
     
  5. Tom J

    Tom J New Member

    They still run so it's off the tank in the loft...
     
  6. DIY0001

    DIY0001 Active Member

    Then it would appear that you have some blockage in the pipe from the tank. You may have dislodged some gunk in the tank when you moved it and it is caught in the pipes.
    If you are really careful to avoid overfilling the tank, then you could try to dislodge it by connecting a hosepipe from the mains to the tap and open both for about 10 seconds.
    Make sure the tank overflow is working properly first.
     
    Creek likes this.
  7. Tom J

    Tom J New Member

    Thanks I'll try this first thing tomorrow morning
     
  8. terrymac

    terrymac Screwfix Select

    If your hot and cold taps are the same poor performance ,it's unlikely that you have blocked both . Exactly how much have you raised the height of the cold tank ? If you raise it 1 metre ,that would result in increased pressure of only 0.1 bar ( one tenth of a bar ), but introducing restrictive elbows would reduce the flow ,so the overall effect would be a negative one.
    Don't confuse pressure and rate of flow , they are different things. Your gravity plumbing system is low pressure ,and in order to get the best flow rates ,the supply pipework has to be the right size ,22 mm direct to the bath , for instance , isolation valves must be FULL bore , flexible hoses to taps should be taken out the equation,and monobloc taps avoided. Tap selection should be ones suitable for low pressure systems.
    If you have gate valves ( big red round wheel head) and you have closed/ opened them whilst working on the tank , they may not be fully open ,dreadful things !! Replace them with full bore lever operated ones.
     
    Last edited: Feb 15, 2020
  9. Tom J

    Tom J New Member

    Thanks for the help. I have full bore valve installed now and the issue is poly pipe in the walls I believe. My only hope now I suppose is to change both basin and bath taps to see if that can have any effect?
     
  10. terrymac

    terrymac Screwfix Select

    What type of basin and bath taps do you have ,and are they connected to supply pipes with flexible hoses ?
     
  11. Joe the Plumber

    Joe the Plumber Screwfix Select

    Just a thought. After you raised the tank, did all the outlet pipes slope slightly downwards?

    If they slope even slightly upwards, you may have built in air locks which can be a blighter to remove and will adversely affect the flow.

    I've one customer whose place I know to never drain down as it can take hours to get rid of the resulting air locks, but they still won't have the pipework altered to sort it out.

    If you've got one, you could try sucking water through the taps with a wet and dry vacuum. As long as you're sure no debris ended up in the pipes of course.

    And make sure the water level in the cold tank is high enough.
     
  12. Tom J

    Tom J New Member

    They all definitely slope. To make the copper pipes work I had to put a 135° on them. The rest all certainly slope downwards.
     
  13. Tom J

    Tom J New Member

    They are mixed taps. The bath is straight onto copper pipes. The sink is copper until the fittings for the tap which are the silver hoses
     
  14. terrymac

    terrymac Screwfix Select

    Ok , looks like the basin tap isn't suitable for low pressure gravity plumbing system. Does the bath tap have a shower hose attachment ? Is the pipework to bath taps 22 mm ?
     
  15. Tom J

    Tom J New Member

    Bath does have a hose attachment. Only works when you twist the bath tap to the side and move the mixer tap other way. It is 22mm all the way to the bath.
     
  16. terrymac

    terrymac Screwfix Select

    When using bath taps to fill the bath how poor is the flow ? Put both hot and cold taps on full ,run water into a bucket or similar for 1 minute ,and measure how many litres you get.
     
  17. Joe the Plumber

    Joe the Plumber Screwfix Select

    Just to confirm, is the water level in the tank okay?
     
  18. Tom J

    Tom J New Member

    Yup right up to the float at top not far off the overflow
     
  19. Tom J

    Tom J New Member

    Will do this in 10 minutes for you
     
    terrymac likes this.
  20. Tom J

    Tom J New Member

    Cold is 1.3litres and hot is 2.2 litres. Cold definitely used to be quicker before raising the tank. So was probably around 2 like hot before
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice