Issue with hot water

Discussion in 'Plumbers' Talk' started by Farrukh, Aug 8, 2018.

  1. Farrukh

    Farrukh New Member

    Hi All

    I have an issue with the shower which is driving me mad and hopefully someone would be able to point me in the direction. Few weeks ago my shower started to pulsate a bit (water coming out slow than fast for first couple of seconds). Over the period of couple of weeks, it has gone really worse and pulsating now for first 3 or 4 minutes.

    In terms of setup, I got my cold water tank in the loft and below that, I got my immersion heater tank, then I got a twin impeller gravity fed pump which only connects to the shower. I can hear the pump pulsate as well.

    When this problem started, I tried leaving the shower head on the floor to see if it makes any difference, but nothing. Now, when the problem has gone even worse, I tried it again i.e. leaving the shower on the floor. This does make a bit of difference i.e. it does pulsate for couple of minutes and then a steady flow unlike pulsating for 3-4 mins and than steady flow.

    I was initially thinking that it could be a shower head or the shower hose. So, last nite, I took the shower hose off and turned the tap on, but it was doing the same thing. This means the hose and shower head are fine?

    I also noticed that hot water flow in all the taps is not as fast as the cold water.

    Please point me in the rite direction so I can have my shower in peace!

    Many thanks
  2. Pollowick

    Pollowick Well-Known Member

    Airlock, failed pump, partial blockage, thremostatic cartridge failing ...

    What pump is it (exactly)?
    Farrukh likes this.
  3. Farrukh

    Farrukh New Member

    its Mira 1.5 bar twin impeller...dont have the exact model number with me at the mo
  4. The Teach

    The Teach Well-Known Member

    have a look at the pump manufactures internet site,they will have some trouble shooting tip's :)
    Farrukh likes this.
  5. Allsorts

    Allsorts Well-Known Member

    Hi Farrukh.

    The hot water flow from a gravity system like yours won't tend to be as fast as the cold as it has the added friction of having to pass through some serious bends and a hot water cylinder.

    Do you think the hot water flow from taps is less than it was before? Ie, is there something causing a more-than-expected reduction in the hot flow?

    Does the hot tap 'splutter' at all - cough out blasts of air? Does the shower do this? Or does the shower just pulsate?

    If there are 'coughs' and 'splutters', then that indicates there is air being drawn in, and this most likely would be on the hot water side, again most likely down the vent pipe. This can be due to a reduced flow from the cold tank to the hot cylinder, so it isn't being replenished as quickly as water is being pumped out - so it sucks down the vent pipe instead.

    Does your hot cylinder have a flange fitted at the top? Please post a photo if you don't know (keep it below 2MP).

    Basically, tho', a pulsing pump - if it isn't simply faulty - is a common indication of an inadequate water supply to it - partial blockage somewhere, etc.
    daviduong and Farrukh like this.
  6. Farrukh

    Farrukh New Member

    Hi Allsorts and all

    Thanks for your replies.

    I have noticed the pressure from the hot tabs is bit lowers that what it used to be before. Also, I have not noticed any splutter coughs etc from the shower or the taps.

    I am not sure about the flange. I will take a picture tonite and post it here.

    Thank you all once again for your help.
  7. Allsorts

    Allsorts Well-Known Member

    A photo would be good.

    If you could also look in your larger cold water storage tank in the loft and see what state it's in - clean water or bits of muck - that could be a clue.
    daviduong and Farrukh like this.
  8. DIYDave.

    DIYDave. Well-Known Member

    Check the inline filters to the pump, may need a clean out

    Easy job, should be isolator valves on both hot and cold feeds, 10 minute job

    Is there a filter in the shower as well ?
    daviduong and Farrukh like this.
  9. Farrukh

    Farrukh New Member

    Hi DIYDave
    Not sure about the filter on shower. Its a standard Mira shower head from screwfix.
    I will check the filters on the innlet side though and clean them. I think there are isolators on the inlet side, but will double check first.

    Thanks for your help
  10. Dennisplamer

    Dennisplamer New Member

    This normally happens due to either a scaled up shower head, a blockage in the hose or a blockage in the shower valve.
  11. Farrukh

    Farrukh New Member

    Please see the pic of the top of the cylinder.

    What i just niticed is that i just tried to isolate the inlet for hot and cold. I tried taking the hose off the pump and hot one was still flowing. Half a bucket was filled and it was still flowing. Seems like the stop cock is stuck? Could it be a cause?

    Attached Files:

  12. DIYDave.

    DIYDave. Well-Known Member

    Without wishing to state the bleedin obvious, the pump is supplied via the white plastic pipe, yes ??

    Where does the other end of that copper pipe go to ?

    Shower and pump specs will usually suggest that a dedicated hot and cold supply is required for correct operation, looks like that hot supply is feeding two outlets

    Your ‘stopcock’ is actually known as a Gate Valve (but yes, essentially a stopcock) :)

    Gate Valves are notoriously s hit with frequent failures, generally only making themselves known when you need to shut off water !

    They seize up internally and either don’t fully shut or don’t fully open. Excessive force to fully open/close may well result in spindle shearing off

    Change gate valve to a ‘full bore lever valve’. SF sell em, Pegler brand very good. Knock off copies few quid cheaper but are that same quality ? Who knows ?

    In meantime, turn off cold feed to hot cylinder (if fully working) and that will simply stop the hot from coming out of cylinder

    This is a ‘work around’ whilst gate valve is knackered. But best to change valve for long term ease

    Let us know how you get on :)
    Farrukh likes this.
  13. Farrukh

    Farrukh New Member

    Hi DiyDave
    Thanks for your help.
    Its not a dedicated line for the shower for the hot water. Saying that, it was the same configuration before and it was working fine :(

    I will replace the gate valve :)) with full bore lever valve tonite. Could this be the cause of the issue you reckon?
    Also to change the valve, do I need to empty the hot wayer tank or just shut the valve between the cold water tank going towards the bottom of the hot water tank as you suggested?

    And yes the picture was not clear but the speedfit is going to the pump
  14. Farrukh

    Farrukh New Member

    please have a look at another pic

    Attached Files:

  15. DIYDave.

    DIYDave. Well-Known Member

    I’m not in the building trade myself but only know what I know from doing up several houses myself and learning ‘on the job’ (and lots of reading) :)

    The gate valve ‘may’ appear to be fully open but in reality, it may be slightly restricting water flow and causing ‘water starvation’ at the pump, causing it to pulse (perhaps)

    As above, change for Full Bore Lever Valve as you know it’s faulty and not fully shutting off hot supply

    As long as you can fully turn off cold feed to cylinder, this will stop hot water coming out the top. It’s the cold flowing into cylinder that pushes out the hot

    Switch off power to pump and cold feed, then open up shower and whatever else that hot pipe feeds. This will reduce any pressure and water in hot pipe, then remove gate valve. There will be a little water dribbling out but ur in the loft and ur gonna have plenty of cloths with you so no problem

    Don’t forget to check inlet filters on pump

    If this still doesn’t help the shower flow, I’m outta ideas but at least uv got a nice new shiny lever valve :)

    Have you checked the shower head, does it look a bit scaley ?

    Don’t wish to criticise but you have a lot of unsupported pipe work there, must have been a worldwide shortage of pipe clips during the install ;)
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  16. Allsorts

    Allsorts Well-Known Member

    Your CWS is right above the hot cylinder. That's good and bad. The good is that the supply from the CWS to the bottom of the hot cylinder is very direct and, apart from the gate valve and a couple of elbows, theoretically without restriction. The bad is that you have very little 'head' - height of the CWS above the cylinder.

    This means that if you assist the draw of the hot water - ie use a pump - then the natural 'stored' pressure of the CWS which is needed to replenish the hot cylinder is going to be borderline. Ie, if you suck hot water out too fast, then the gravity refill from that CWS will not keep up; this will make the pump also draw the contents of the vent pipe right down which could introduce air - tho' you say there is no spluttering.

    You do not have a flange fitted on that cylinder, which is a shame - it would very likely help.

    From the top of that cylinder is the white pipe supplying the pump, and also a copper pipe heading off - that copper pipe will likely split vertically with the downwards pipe going to other taps in the house and the upwards pipe being the 'vent' I mentioned before - this should go up and aim down in to the CWS.

    What I suspect is happening is - when the pump fires up, the instant 'draw' not only pulls hot water out of the cylinder but also pulls the water in that vent pipe (which, when static, sits at the same height as the top of the CWS water level) right down very quickly. When it reaches its lowest point, it 'bounces' back up - this cause a momentary back-suction which marginally slows the pump. The water column reaches its max height and then plummets again - this causes a 'gush' in the pump. The cycle repeats = pulsing. (I'm assuming the pump doesn't actually fully switch off each time it pulses?)

    Hard to pinpoint the actual cause since I reckon your whole system was operating on a fine margin at the best of times, so it would only take a small change to send it cycling.

    Replacing that gate valve is obviously a must since it's stuck, but I doubt it's the cause - why should it be? While you are at it, I'd personally also replace the gate valve between the CWS and the bottom of the cylinder - this one MUST be fully open and free-flowing or it WILL cause problems.

    The replace this other gate valve you will need to stop the flow from the CWS - this can be done by emptying it or by simply plugging the outlet inside near the bottom - a wine cork will probably do. Then you must also drain the hot cylinder down to the level of that gate valve - which is not far.

    You still haven't told us the state of the water in that CWS - if it's dirty, then drain and clean it out fully. Then make sure it's fully covered.

    Any chance of easily raising the height of the CWS? And a flange in the hot cylinder is recommended, although you clearly managed without it before.
    Farrukh likes this.
  17. Farrukh

    Farrukh New Member

    Good morning all..!

    Thanks DIYDave and Allsorts for your help and support so far.

    So, I tried changing the gate valve on the hot inlet side last night. I turned off the gate valve from CWS to hot water cylinder and pump unplugged. Then I turned off the gate valve which is feeding from hot water tank to the pump (the faulty one). I took the hose out of the pump and it was still flowing ...duhhhh!!!!! So, I thought to let it flow for a bit and see if the pressure reduces. But it did not!
    I have to drain the system down I guess and as you guys suggested change all the gate valves. Job for the weekend.

    I have checked inside the CWS and I cant see any dirt floating around. Its covered as well.
    Allsorts likes this.
  18. Allsorts

    Allsorts Well-Known Member

    When you remove the faulty gate valve (the one on the hot outlet from the top of the tank) then you would expect water to flow for a short while - while the water in the vent pipe drain away - but it should have then stopped. As you've sussed, the fact it carried on flowing suggests the other gate valve - the one on the supply from the CWS to the bottom of the tank - is also faulty. So, yes, it's a drain-down...

    Make sure you full full-bore lever ball valves.

    Hmm, no obvious dirt in the CWS? Not sure what else to suggest, then. When you drain the hot cylinder (this actually only needs doing down the the level of the second gate valve) have the contents going in to a bucket so you can monitor if there's any debris in it.
    Farrukh likes this.
  19. The Teach

    The Teach Well-Known Member

    usually the pump manufacture requires the shower pump feeds and outlets to be 22mm ;).
    On the hot connection,An essex (no stop) flange into the cylinder 22mm copper pipe to the pump will prevent a lot of air being drawn into the pump.then the cold will need to be run in 22mm. Preferably with the ball valve connection on the opposite side of the cold tank.

    Ensure the water tank does not empty when using the shower.

    Pipes will need to be supported,the flexible shower connection pipes should be as straight as possible.They can kink and cause insufficient water flow as in your photo on the pump cold side.

    any high level pipes will benefit from having a means of releasing air,have a look at the installation literature.

    Farrukh likes this.
  20. Farrukh

    Farrukh New Member

    Hi All

    First of all massive thank you to everyone for you help here. Now please bear in mind that I am new to all these DIY, pumps, plumbing etc as its my first house (all good learning so far). So, I was bit under the pressure from the other half to fix the issue asap or call the plumber. So, had to call in the plumber. After spending some time, he managed to point it to the shower it self (not the hose or the shower head) but the shower unit - not sure what you call it!. Anyway, he took it out and washed it and there were pieces of wood stuck inside the shower :S. He gave it a good clean and it works like a dream now. Now, as I said, I am new to all these, I might have said before that I changed the shower, but it was the shower head!

    Anyways, thank you to everyone once again and I just thought that I let everyone know the latest as its a good learning for someone new to DIY like myself
    Heat and Allsorts like this.

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