No hot water to bath taps in main bathroom unless ensuite tap is turned on at same time :-/

Discussion in 'Plumbers' Talk' started by JoBlount, Nov 1, 2017.

  1. JoBlount

    JoBlount New Member

    Hi. I apologise for the long post, I have no plumbing knowledge and want to check that the information the bathroom fitter has given is correct. We have recently had our main bathroom refitted with the addition of a stand alone shower, powered by a new twin positive head pump (gravity fed system with cold water tanks in loft and hot water cyclinder in airing cupboard on same level as bathroom). Bath tap was changed from an old mixer to a freestanding thermostatic mixer and sink already had a mixer tap which was replaced with similar. The old bathroom and separate ensuite shower were already serviced by an existing 2 bar pump, so with the addition of the extra shower a second pump was added just for the new bathroom shower alone. Prior to the refit the hot water in the bathroom was too hot coming through the tap but did flow with good pressure from the pump. After the refit all was ok for a month but now we have no hot water in the main bathroom when we turn the bath or sink hot tap on, unless we run to the other end of the hall and turn on the hot tap in the ensuite at the same time. Cold is fine. Called the fitter back today and he said we need to buy a more powerful pump (4 bar which is very expensive) as he thinks the issue is that the bathroom is further from the cylinder than the ensuite and so pressure is not enough to kick the pump on. I don’t understand this as before the bathroom was refitted all was fine and the pump worked fine (we have installed the new shower with its own pump this is working fine so don’t see that this is connected). I don’t want to pay out for a new more powerful pump if that is not actually the issue. We paid a lot of money for the work and I’m unhappy that this was not told at the time but clearly we need to resolve having no hot water when we turn the taps on. Hot water in the ensuite is fine and this is serviced by the same pump but is a closer distance to the airing cupboard. Any advice would be greatly appreciated. Many thanks, Joanne
  2. nigel willson

    nigel willson Well-Known Member

    Problems are fitters fault! They should have known how to install so that you don’t have any problems!
  3. JoBlount

    JoBlount New Member

    That’s what I thought but he is saying that’s not the case and that we need to purchase a new pump and pay to have it installed. My view is this may not even resolve the problem. Having read the pump trouble shooting guide, it sounds like the issue is that there is insufficient water flow to start the pump as opposed to the pump not being powerful enough. What do you think?
  4. CGN

    CGN Well-Known Member

    Just to clarify, is the pump just for the showers?
  5. Can you confirm - the actual bath and basin and their pipework are as they were - except they have both had new mixer taps, the bath being a therm mixer? And this is supplied via the 'old' 2 bar pump?

    And in this bathroom you have had a new 'stand alone' shower cubicle fitted and this has its own brand new pump? Phew - two bludy pumps for one bathroom, eh? (Why?)

    The new shower cubicle - where is the pump fitted and where do the H&C pipes join to the main bathroom's pipes?

    Anyhoo, is there anything we can speculate on here? The old bath and basin taps ran fine on the same old pump as now, but you have now replaced both sets of taps - which did work ok to begin with, but now doesn't? I wonder if the new taps have a greater pressure requirement than the old, so are slightly more restrictive to flow - ergo they were 'borderline' from the off (in being able to turn the pumps on) and now, for some reason, are worse - so the pump fails to fire.

    Is the basin mixer also a thermo type? Can you turn on ONLY a hot or cold with the bath and basin taps? Are you saying the pump fires for cold but not hot? What if you turn on the bath hot and the basin hot at the same time?!

    (Since the pumps are 'twin', why can't you get it started using the cold taps and the hot then joins in? Why do you run to a different bathroom for this? Or am I confused...)

    As you suspect, this does sound like an inadequate 'triggering' flow, but the reason could be either a more restrictive tap (being thermo) or a slightly more lazy pump switch. (Or even debris in the system).

    Ok, I also cannot see how a more powerful pump will sort this! A 2-bar pump is plenty, and all it needs is simply to be able to fire up; a 4 bar pump ain't going to fire any faster! Surely?

    Ok, perhaps a negative-head pump would be better? These operate on a lesser triggering flow (<1 lpm - at least that's my understanding, but I actually know very little about these things).

    Something I don't get - why did your shower require a separate pump - why not one for the whole bathroom - after all, you ain't going to be running a shower and a bath at the same time, are you?

    Anyhoo, if the old bath and basin taps were separate H&C, then I can imagine mixers - especially thermo ones - having a slightly 'reduced' - more restrictive - flow, so if the gravity supply is weak (as it must have been) then this may have taken the triggering point to the bare limit. This worked ok for a month, but has now stopped - so it must be fundamentally 'ok', but something has happened to change that, and that could have been a marginal drop in flow, or a marginal reduction in the sensitivity of the shower.

    Again - what happens if you turn on both basin and bath hot taps at the same time?
    Last edited by a moderator: Nov 2, 2017
    JoBlount likes this.
  6. JoBlount

    JoBlount New Member

    No. We have a separate new pump for 1 new shower (working fine) and the old pump is for the bath tap and sink tap in main bathroom and also for the sink and shower in ensuite. Pump functions properly for all of ensuite but not when taps are turned on in main bathroom.
  7. JoBlount

    JoBlount New Member

  8. JoBlount

    JoBlount New Member

    Thanks. Yes we have 2 pumps as that’s what fitter recommended as we are a family of 4 and he said this would then enable 2 showers to be taken at same time (ie. one in ensuite and another in main bathroom). Both pumps are side by side in the airing cupboard which is invetween the bathroom and ensuite (albeit closer to the ensuite). The sink tap is not a thermostatic one like the bath, just an normal mixer. Cold water runs fine on both but as soon as you twist handle for hot the water stops running as the pump is not kicking on. So I leave the tap on, run to the ensuite, then the hot on there and immediately the hot taps in other bathroom come on (and stay on even when I turn ensuite tap off). It’s driving me mental and I feel like I’m being fobbed off now by the fitter as I don’t actually think he knows how to fix it (and my hubby is not a DIY man). The bath was moved in the refit so am guessing some of the pipes were changed and there were lots of issues with the fitter working out why certain things were happening as cold tanks in lofts starter back filling with hot water until he fitted some non return valves on the pipes. Sorry that I am vague but I’ve struggled to understand it all despite reading up on the net. It’s so frustrating to have spent all this money and have these unresolved issues. It was fine for approximately 4 weeks and then didn’t work when we returned from our holiday.
  9. Ok, we can conclude that the old pump is basically working fine, so it must be down to a more restrictive flow from your new taps (or debris)?

    I suspect the new taps have a marginally reduced natural flow, so brought the initial (unassisted) flow level down to barely operational for the pump, so it was 'only just' working with these new taps from the off. Something has deteriorated still further on the hot side - perhaps the pump's flow switch is poorly - and that's enough to make it too insensitive to fire.

    This 'old' pump - it's a twin impeller? Ie - one motor pumps both H&C? If only one tap is opened, the pump tries to pump both 'sides', but can obviously only do one? So what happens if you fire up the pump using the cold, turn on the hot, and then turn off the cold? Does the hot keep running?
  10. So the cold taps (bath or basin) start up the pump ok, but opening a hot - with cold still on and the pump is actually running - makes it stop?!
  11. JoBlount

    JoBlount New Member

  12. JoBlount

    JoBlount New Member

    I have just tried to turn on basin and bath hot tap at same time and nothing except a slight trickle from bath tap. I believe the new shower is coming off the same feed as the pipes that feed the bath as the shower is at the back of the bathroom after the bath. I will check the pipes off the hot water cyclinder tomorrow. I think you are right that the bath tap needs high pressure which the bathroom didn’t have when we moved in (though you could still run a bath sufficiently). We thought having the pump would give the tap enough pressure but as I said my plumbing knowledge is very poor
  13. JoBlount

    JoBlount New Member

    The cold is fine but the cold runs without the pump coming on. I recall the fitter saying the cold is mains fed so didn’t need to be pumped, does that sound correct? Definitely no pump on when the cold water runs
  14. Simply teeing off the existing bath taps to supply the new shower shouldn't really affect the water flow - unless the guy did some extra pipe work - bends etc - which affected the pipe run to the bath.

    Your old pump should provide plenty of performance for your new taps, but only once the pump has actually managed to fire up! And that requires a minimum flow, often around 0.8 lpm or so. If your natural 'gravity' flow is less than this, then your pump will struggle to be operated. And that appears to be the issue here. I cannot see how a more powerful pump will fix this...
  15. JoBlount

    JoBlount New Member

    Yes totally agree and once the old pump actually fires up (from turning on hot tap in ensuite first) then the flow is good. I think he did change some of the pipes as I recall being concerned by the reel of plastic pipes as I always thought pipes should be metal (researched that and apparently it’s a new thing). I am loathed to spend £300 on a new pump as I don’t believe that will help so is reassuring that you agree. Do you have any suggestions please on how we could increase the minimum flow for the hot water? (someone else suggested by installing a combi boiler as they apparently have pressure and negate the need for pumps but don’t have the £5k to switch over to that!!)
  16. Ah. If the cold is supplied by the mains, then that's already at a higher pressure than even the pump provides, so is happy to flow without needing a pump.

    Have to say, I understand it's not 'ideal' to have one side pumped and the other mains; much better to have BOTH supplied via the loft tank. That way the water will be at almost exactly the same pressure to begin with, and then they can BOTH be boosted with the pump by the same amount and at the same time.

    And, this also explains the issue with hot water being forced back up in to the cold storage tanks - this was almost certainly due to the higher-pressure cold mains water meeting the hot water in your bath or basin 'mixer' tap, and then forcing the hot back down the pipe the way it came! I presume the plumber fitted a non-return valve on the hot pipe to stop this happening.

    Hmmm - non-return valves will also add a bit of restriction to the flow, so if the hot was pants to begin with, this valve wouldn't have helped.

    AND, as soon as you turn on the cold tap in the mixer, this will cause a slight pressure build-up inside the mixer tap body, which - again - will make it harder for the hot water to flow fast enough to trigger the pump. This situation would not happen if the taps were separate H and C.

    (Imagine what's happening; you have a hot supply and a cold supply coming in to a single tap unit and 'mixing' there before coming out the tap or shower hose. Imagine now if you were to restrict or block that outlet - the tap's spout or shower hose. What would happen? Yes, you'd stop the water coming 'out', but actually there would still be a flow within the pipes as the greater cold water pressure now forces the weaker hot water back up the way it came... What's more, once the pressure starts acting against the hot, reducing its flow, the pump would shut off. Once off, it's carte blanc for the cold to shove the hot right back to the cylinder and hence to the cold tank. Even if this reverse flow doesn't actually happen, the greater pressure of the cold in the mixer tap will be having an effect on the hot trying to get out. That's why unequal supply pressures is not good.)

    I don't know what the best solution is - hopefully a plumber will come along and suggest something. But, if this were my bathroom and I did have to have pumps (I hate them, but they are sometimes necessary) then I would have supplied the bathroom/showers with a balanced supply (ie a cold feed from the tank) and fitted twin-impeller pumps so that both sides remained at equal pressures.

    Hmmmm - a thought... Perhaps what he's thinking is that a more powerful pump - a 4 bar beauty - will 'counteract' the higher pressure of the cold?! Blimey, that's some awesome pressure you'll be having...

    That might work, but - jeepers - what tangled web. There is a potentially more simple option - he could instead fit a PRV (Pressure Reducing Valve) to the cold supply to the bathroom, to bring the cold pressure DOWN to around 2 bar to match that of the hot. That should balance them.

    But, I'm not a plumber, so I don't know if that's a sensible solution. (It makes ok sense in my head...) What to do? At the very least you need to make it clear to the plumber that if his solution ("we're gonna need a bigger pump!") doesn't work, you don't pay...

    It sounds like a can of worms :(
    Last edited by a moderator: Nov 2, 2017
  17. NB - I am speculating here, so please don't treat it as gospel of any kind :)

    By now you'll have read my previous post - unless you fell asleep - and will see that another solution is to reduce the cold pressure to match that of the hot, and not to boost the hot further to match the cold.

    Perhaps you can run that idea past him? And hope that he doesn't get upset (it's another bit of 'internet' information...!) But, if it makes sense to you, then you can always ask him.

    Looks like all the proper plumbers have gone to bed... :(

    The other solution - I'd have thought guaranteed to work - is to run the cold from the storage tank too, and not from the mains. This is straight-forward stuff (as long as access is ok). But then you'd need a twin-impeller pump to run the H and C at the same time, so two new pumps... (Mind you, 2bar Stuart Turner twin pumps are 'only' around £110...)

    Oh, and 'plastic' pipe is ok - many advantages over copper, tho' they do have a slightly narrower bore...
  18. CGN

    CGN Well-Known Member

    Keep it simple, showers off pump, taps off mains cold and gravity hot.
  19. The Teach

    The Teach Well-Known Member

    My penny's worth,
    so the cold water is supplied via the incoming cold water main and there is no cold fault at the taps/showers.
    No distance has been mentioned between the faulty taps and the hot water pump,the pipe feed needs to be the most direct route,if it loops up from under floorboards to loft level and drop down again then any gravity (unpumped gravity flow) needed to activate the pump flow switch will be lost.
    If the hot pipe run to the faulty taps is as direct as possible with as few bends as possible with decent taps that give some unpumped initial flow.

    Points to consider,on the defective side of the installation only.Assuming you have a single impeller pump.
    Check for possible trapped air.
    The actual hot water temperature needs to be correct,too hot and air bubbles collect.
    Any filters in the pump or taps/shower valve need to be clean.
    Check for debris in the pump.
    Check shower pump flow switch.
    If the other pump is similar it could be temporarily swapped over,see if it works.
    Any Flow regulators in the faulty hot water taps/shower should be removed.
    All isolation valves need to be fully open with full bore capacity.
    Increasing the inlet pipe size to the pump can give the pump a little more gravity force to activate the flow switch,changed a few to 28mm over the years.
    The retrospectively fitted non return valve removed and other back flow arrangement considered.

    Maybe if your plumber :( cannot get it to work ask them to get someone else in at their expense.
    Deleted member 33931 likes this.
  20. The Teach

    The Teach Well-Known Member

    Kiss o_O

    K eep
    I t
    S imple
    S tupid.
    CGN likes this.

Share This Page