Backflow on mixer tap

Discussion in 'Plumbers' Talk' started by R.W_Carpentry, Jul 6, 2017.

  1. R.W_Carpentry

    R.W_Carpentry Active Member

    We've had our water cistern in loft overflowing recently, the float valve seems to be working and today I found the water level considerably higher and it overflowing a lot.
    I believe the problem could be backflow from our kitchen mixer tap, this is the only mixer tap in the flat and has been recently fitted. All taps are mains fed and the loft in cistern just feeds the hot water tank.
    I tested earlier by running the hot in kitchen til pipe was hot then started mixing in cold and the pipe immediately went cold so I'm presuming this proves the backflow issue?
    What would be the best course of action? Can I install a check valve or shall I just change for a different mixer?
     
  2. terrymac

    terrymac Screwfix Select

    just fit double check valve on hot pipework. cheap and easy to fit.if that does not cure it change tap for wras approved one.
     
    Last edited: Jul 6, 2017
  3. R.W_Carpentry

    R.W_Carpentry Active Member

    Thanks, having a look since there's not a lot of pipe on show , will a combined double check and isolating valve be okay or is there any down sides to these?
     
  4. terrymac

    terrymac Screwfix Select

    one possible downside on the plumbing system you have is the cold mains pressure is much greater than the hot. as I understand it your cold water cistern is in the loft ,and I assume your flat is on one floor ,directly under the loft. it is the height of that cistern above the outlets (taps) which determines the hot water pressure . so via your mixer the cold pressure may prevent a check valve from opening to allow hot to come thru . a kitchen mixer tap should not allow hot and cold to mix in the tap body.they should only come together at the spout. wras approved taps have to meet this criteria. unfortunately when internet purchases are made you don't know what you are getting very often. did you get yours this way ? probably the best thing to do if pipework is short ,would be to change the tap. regards terry.
     
  5. R.W_Carpentry

    R.W_Carpentry Active Member

    Yeah that's basically the set up, the tap was from B&Q, they no longer sell it now though. I can get access to more pipework, it's just currently they come through quite neatly through the base unit and then that's straight onto an isolator and the flexi for the tap. I may try a check valve as aesthetically I like the tap but pressure isn't great like you say so may have to change it but for a few quid initially I'll try the valve first.
     
  6. terrymac

    terrymac Screwfix Select

    by the way is your hot water excessively hot ? for instance if you turn it on ,let tap run for 3 mins , can you then put your hand under and keep your hand under the running hot water for 1 minute without getting very uncomfortable ,or burned ?
     
  7. R.W_Carpentry

    R.W_Carpentry Active Member

    No temperature is fine , can't remember what it's set for on the thermostat but certainly comfortable.
     
  8. terrymac

    terrymac Screwfix Select

    OK sounds good. reason I asked .....as water heats up it expands and raises level in loft tank. excessive temperature = excessive expansion. I suspect the raised level in loft tank is not solely down to your mixer tap. I would re look at the ball valve. if you hold it up manually ( closed position ) and watch carefully for any dripping .if it continues to drip ,it is not shutting off completely and will raise level.
     
  9. R.W_Carpentry

    R.W_Carpentry Active Member

    Ok Thanks, I've actually got a new float valve that I was going to fit when I first noticed it overflowing but didn't look like it was down to it in the end but I'll fit it anyway at the weekend since I've got it, the current one is a part 1 that's had to be bent quite a bit to stop water getting close to the overflow so I've got a part 2.
     
  10. terrymac

    terrymac Screwfix Select

    good idea.
     

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