low pressure in all hot water taps

Discussion in 'Plumbers' Talk' started by homegoat, Jul 12, 2018.

  1. homegoat

    homegoat New Member

    hi folks
    been like it for as long as I can remember
    cold water taps all have lovely pressure (and the toilets)
    but the hot taps pressure is not very good
    I've changed the feed pipe from the cold water tank to the water cylinder to 28mm to increase the feed,
    water cylinder has been in at least 35 yrs
    if I connect the cold water to the hot water (to clear out any air, I use the pipe on the washing machine)
    then remove the pipe
    the pressure in the hot taps is a lot better
    I did read some time ago that the problem could be that a piece of foam insultion fell into the water cylinder when it was installed and its that that blocks the flow ?
    the water cylinder outlet connector feels as if it will sheer off if I try to hard to move it
    any suggestions please ?
    if its a new water cylinder, what type to get ? at the moment its a copper cylinder 1250 X 450 indirect vented
  2. Pollowick

    Pollowick Well-Known Member

    Air in the system ... how and why?

    What pipe work do you have from cold water storage to cylinder? You say 28mm, but where does it run? Does it have any significant horizontal runs and are these slightly downhill? Check those out - I ask that as when I moved here we had the same issue. A previous owner had decided to install a gate valve in the cold feed to the cylinder and chose to fit it in the vertical run. Rather than cut out 50mm of pipe, they cut the pipe and pushed it up resulting in the horizontal run from storage to vertical drop having a rise. Slowly, small amount of gas would create an airlock in the corner, once I found the cause, just cutting out a small length of pipe was enough to restore the flow.
  3. kiaora

    kiaora Well-Known Member

    I sounds like the fitting on top of the cylinder has scale build up and reduced the outlet size,
    Are you able to undo just the nut holding the pipe to the top of the cylinder?
    If so, take it off and have a good look/ poke about, to see if blocked by scale etc.

  4. homegoat

    homegoat New Member

    28mm from cold water tank to cylinder, just over 2.5 mt drop with 3 right angle bends, total pipe length about 3.5 mts. before I fitted the 28mm pipe it was 22mm pipe with same run, (I fitted the 28mm pipework incase that improved the hot water pressure from the cylinder, but it had no change

    tried to loose that top holding nut, would move at all,
    thought about release agent (WD40 etc) but thought the smell would go into all the towels etc in airing cupboard, so dismissed that idea
    what I don't want to do is damage pipes/cylinder ad have not hot water until I replace them
    I guess what I need to do is bite the bullet and get a new cylinder, but stainless or copper ?
  5. Pollowick

    Pollowick Well-Known Member

    Or do you have an immersion heater fitted on the top of the cylinder?

    If so, try to remove that. Start with the right spanner and the tank full, then once it starts to move and maybe seep, drain water off to below the level of the hole. Remove heater and with a decent torch, look to see what scale is in there or anything floating around.

    If the cylinder is clear then the problem could remain in the pipe work. Don't buy a new cylinder until you have proved it - expensive and time consuming to replace it.
  6. Dr Bodgit

    Dr Bodgit Well-Known Member

    Sounds to me like its likely scale clogging things up too.
  7. homegoat

    homegoat New Member

    I've tried removing the immersion heater but it does move
    don't want to go over board with the force in case damage the cylinder
    that's why I was thinking about a new cylinder
  8. DIYperson

    DIYperson Member

    I had a problem some years ago where the hot water at the bath tap would start off OK and then the flow would reduce. It turned out that the sacrificial anode in the hot water cylinder had disintegrated and left a couple of large plastic "penny" washers floating around. When water was drawn from the cylinder, one of the washers would float across the outlet, restricting the flow. 2009 DSCN0872.JPG
    homegoat likes this.
  9. Are you comparing cold water from taps that are fed by mains water pressure against hot water from taps fed by your gravity hot water system? If so, then of course hot water flow will seem poor in comparison to cold water flow.
  10. Pollowick

    Pollowick Well-Known Member

    Get the spanner on it and gently tap in both directions ... three or four to unscrew, three or four to tighten, three or four to unscrew, three or four to tighten, three or four to unscrew, three or four to tighten, three or four to unscrew, three or four to tighten, ... nothing to hard you are just trying to break the seal, tapping back and forth should finally loosen it.
  11. homegoat

    homegoat New Member

    I'm comparing the cold water taps fed by the cold water tank, so its almost like for like (as the same feed pipe also feeds the cylinder

    I'll give it another go with trying to remove the immersion heater element, as I say its all been in place 35+ yrs, so maybe I've had my monies worth from the hot water cylinder
  12. Pollowick

    Pollowick Well-Known Member

    Mine has been in for over 25 - and last year I removed the element, a little tapping and coaxing and it soon came out. Yes, you may have had your money's worth but if that is not the problem then you will be £500 poorer and still have an issue.
    homegoat likes this.
  13. The Teach

    The Teach Well-Known Member

    are the original water taps still in use ? you know the ones designed for historical uk low pressure hot water supply.
    Last edited: Jul 12, 2018
  14. homegoat

    homegoat New Member

    I've replaced all the taps, and most of the pipework
  15. Pollowick

    Pollowick Well-Known Member

    What are the taps like? Are they suitable for LP - with a minimum 0.3 bar requirement?
  16. homegoat

    homegoat New Member

    no idea what the taps are

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