Mains feedback up hot feed.

Discussion in 'Plumbers' Talk' started by GrahamB, Dec 13, 2004.

  1. GrahamB

    GrahamB New Member

    Electrical Engineer – DIY everything else! Have just finished refurbishing a bathroom - tiling, under-floor heating, Ideal Standard ‘arm-and-a-leg’ Sottini suite etc. (The brassware is quite nice, but still waiting for the third close-coupled WC pan with a flat top that couples without leaking!) Lots of problems but now mainly sorted, I hope.
    These continental style mixer taps are a bit disappointing - bath taps reduce to 15mm and basin monoblocs reduce to 10mm, so without a pressurised system the hot water flow is significantly reduced. Which brings me to the problem:
    Bungalow – 6ft head of water - the bathroom is at the end of a 10metre run - mains-fed cold – gravity hot – common 22mm feeds to bath then 15mm to basin and WC.
    Question - how best to stop the cold main feeding back up the hot feed on the basin and the bath hand-shower? Reducing the cold flow via the service valves is noisy and counter productive.
    Would a check valve anywhere in the common 22mm hot feed, say up in the loft, do the trick?
    (I have not worked out why a similar monobloc basin mixer earlier on the same common feeds does not suffer from the same problem?)
     
  2. Jimbo

    Jimbo Screwfix Select

    My understanding is that you need check valves. Personally I have tended to put double-check valves under each mixer, rather than a single one but I don't see why it wouldn't work.

    Another option might be to tame the cold pressure?
     
  3. screwfox

    screwfox New Member

    The fitting of check valves is a requirement of the building regs, but usually to stop hot water feeding the cold water mains system. I would fit check valves on both hot and cold feeds to the monoblocks.

    HTH
     
  4. mj

    mj Guest

    just a small point , did the tap instructions say 'suitable for high pressure only (& or) balanced hot & cold pressure'!
     
  5. mj

    mj Guest

    Balanced hot & cold is the answer, trying to reduce mains pressure & keep reasonable flow rate ain't really practical.
    Change the cold feeds in the bathroom to gravity from the tank is the first option. If you do this first & flow rate is still to slow, then it's relatively easy to fit a pump to the gravity supplies as a booster (1.5 bar will probably suffice).
     
  6. GrahamB

    GrahamB New Member

    Thanks to all for the advice, sorry for the delay in acknowledging, the site would not let me post replies for some reason!
    I have bought a 22mm check valve and will try it in the common hot feed. It looked to me that the spring was too strong to work with only a few feet of head, but it seems to be OK when connected on to the hot tap so I will give it a try. I do not particularly want to connect the cold supply to gravity feed, I only have a 25 gallon cistern and a large bath!
    I am sure you are all correct that I should also have check valves in the cold supply!
     
  7. GrahamB

    GrahamB New Member

    Finally got around to fitting the check valve in the common 22mm hot feed in the loft. As I suspected, the spring on the valve was too strong for the 8 feet head of water, which was reduced to a trickle. So took it out and will do without it. My wife says she can adjust the mix to avoid cold backflow, which is good enough for me.
    Incidentally, I re-read the instructions for fitting a Sottini monobloc basin tap, which say that the hot tap MUST be the left hand tap although it does not say why, other than the ceramic inserts are different.
    Needless to say I had fitted mine the other way round, because it suited the pipe configuration, but I have just reversed them to be on the safe side.
    Does anyone know why they are so insistent on this?
     
  8. britishblue

    britishblue New Member

    The reason the tell you to fit it a certain way, is that the water is mixed just as it exits the spout. The hot water is in the central tube and the outer tube encircling it contains the cold.

    BB
     
  9. MR MISTERY !

    MR MISTERY ! New Member

    Hi GrahamB,
    The reason for HOT on the LEFT and COLD on the RIGHT, is so that VISUALLY IMPAIRED people will know instinctively which is which. I Hope all Plumbers and Diy'ers will remember this in future. This rule is older than most of us.
     
  10. D.E.B.S

    D.E.B.S New Member

    did not know that MR MISTERY ! but i always put the hot tap on a bath closest to the wall so little kids/babies can not reach them and scald themselves. is this ok to do still ?
     
  11. bathstyle

    bathstyle Active Member

    debs, you'll be better off putting hot on the left at all times.
     
  12. bathstyle

    bathstyle Active Member

    just turn the bath around!
     
  13. MR MISTERY !

    MR MISTERY ! New Member

    Hi D.E.B.S,
    Seems like a nice idea,( really kids should not be left unattended anywhere ) but kids do grow up and family's move homes. Its best to stick to the rules on this one.
    Sadly enough visually impaired people are injured by this rule NOT being adhered to.
    Spread the word, it helps.
     
  14. LeeKing

    LeeKing New Member

    Or upside down.

    I'll get me coat.
     
  15. LeeKing

    LeeKing New Member

    Seriously, Mr Misery is correct. I have scalded myself where taps are wrong way round and I've got 20/20 vision!

    I naively always expect everyone to follow the rule but clearly they don't. My house has been installed the wrong way round and I had to show my kids when we moved in because they had got used to HOT on LEFT, COLD on RIGHT and we all get into habits and do things on autopilot and that's when you can get scalded.
     
  16. MR MISTERY !

    MR MISTERY ! New Member

    Hey, that's 'MISTERY'.......
     
  17. MR MISTERY !

    MR MISTERY ! New Member

    cheeky scamp.
     
  18. D.E.B.S

    D.E.B.S New Member

    thanks for the info guys i will now fit them as so ;)
     
  19. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    "My house has been installed the wrong way round"

    Surprised you managed to get indoors at all through the front door at the back of the house with the front door key !!!!!! ;)

    Handyandy - really
     
  20. LeeKing

    LeeKing New Member

    Mr Mistery - sorry mate. Must renew my membership to the D.N.A (National Dyslexia Association).
     

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