Help with hot water airlock....

Discussion in 'Plumbers' Talk' started by HomeAutomation, Apr 18, 2018.

  1. HomeAutomation

    HomeAutomation New Member

    Guys - firstly - sorry for the long post!

    I would appreciate some advice regarding the reoccuring airlocks that limit the upstairs hot water flow in our home.

    Boiler is conventional, with indirect HWT in bedroom cupboard and CWT in the attic - with about 1.5m head.

    The house is/was a new build in 1998, 5 bedroom.

    Cloakroom, utility room and kitchen downstairs - hot water is ok in these rooms - never affected by air.

    Bathroom and ensuite upstairs with power shower all suffer gradually worsening airlocks since house was built.

    I fitted a valve between the hot and cold (mains fed) tap in the utility room (dont want to soak the place using the mixer tap!) and use this to get rid of the air....used to be about once a year, but now needs it every few weeks.

    I am at a loss as to how and why the air is reoccurring after a period of time.

    I have struggled to trace the route of the hot water pipes from the tank to the upstairs taps - it appears to go through the cupboard wall....and then not up to the attic but looks like it then drops down to floor level - the cold feed does go up, but not the hot! I can only assume the hot goes down to floor level and is distributed that way.

    I fitted a surrey flange on the hot water tank - incase that was causing hassle.... but it made zero difference.

    The hot leaves the tank on 22mm...

    I am considering as a last ditch re-plumbing all the upstairs hot water "consumers" - but thats a ball ache as you can expect, as I feel its the only way to get rid of the problem.


    Any ideas as to how its plumbed or indeed, more importantly, why is air being introduced?


    Thanks in advance

    David
     
  2. dcox

    dcox Screwfix Select

    How big is the CWS tank in the loft? Any chance that it's not keeping up with demand from a bath or shower via the cylinder and allowing air to be drawn down the cold fill?
     
    retiredsparks likes this.
  3. retiredsparks

    retiredsparks Super Member

    Do simple checks.....CW flow to attic.
    Ballvalves working full bore(no blockages)
    Tanks outlets all clear....no rubbish in bottom of tanks.
    Also look at the power shower setup........plumbers may be able to give heads up on that area.
    Rs
     
  4. HomeAutomation

    HomeAutomation New Member

    Thanks Both for your replies!


    Tank looks like its 40-50 gallon size, and the tank's level is not dropping - we have cracking mains cold water pressure here.

    There is one gate valve (at the CWT) between cold tank flow and hot tank entry and about 3-4m max of 22mm pipe.

    No debris in the tank - I cleaned it out a year ago to ensure there was no debris of any sort... and have checked it since to ensure nothing is blocking the exit or indeed the ball cock was not sticking letting it run empty. It has a sealed lid... no pigeons(!).

    The power shower is the *real* hassle, in terms of grief from my better half....as you can imagine the air is blue when she gets a poor shower in the morning! Weirdly the two 15mm feeds to the power shower both exit the shower in an upwards direction, but above the shower in the attic, only the 15mm cold appears (fed from the CWT)... the hot must go up and then divert left inside the stud wall to the pipe box near to the sink. Heaven knows why they did not go straight up as it would be a 4-5m run from the HWT.

    I wish I could trace the pipe runs to see where the inevitable issue lies... I dont want to end up cutting many access panels into walls and pipe boxes to find the run. I have never had much luck tracing pipes behind walls with test meters - cables yes, but not pipes...maybe I need a better meter!

    I did wonder about opening the wall near to teh shower, and putting in a new feed from the tank to the power shower. I was concerned though over capping and leaving a "dead" leg... thinking if air got in there, it coudl lead to all sorts of issues.

    I am gobsmacked why the original installer did not bring both hot and cold along together given the respective tank positions.


    David
     
  5. terrymac

    terrymac Screwfix Select

    What size is the pipe from cold water tank in loft to hot water cylinder ,if it is 15 mm replace it with 22 mm ,and get rid of the gate valve and replace it with a full bore lever operated valve. I suspect the power shower is pulling water out the cylinder ,and vent pipe, faster than it is replenishing and allowing air in thru the vent pipe.
     
  6. retiredsparks

    retiredsparks Super Member

    chat to neighbours !
    Might have had similar issues.
    Rs
     
  7. HomeAutomation

    HomeAutomation New Member


    Hi - thanks for your reply.

    The pipe run from CWT to HWT is all 22mm copper. I will replace the gate valve - I guess every little helps with gravity feed!

    Is there any way I can confirm if the air is being pulled down the vent pipe? I have an IR thermometer but dont think the pipe temperature would react quickly enough to prove anything.

    Am I right in thinking the natural water level in the vent pipe will be the same as the water level in the CWT?

    David
     
  8. HomeAutomation

    HomeAutomation New Member


    Hi

    There are three houses in the street like ours and I think they are all different in internal layout...certainly one next door two bedrooms knowcked into one and a bath in the bedroom.

    The three houses of the same type all have long term owners, so I am not aware of them having issues...but will definatley ask.

    I will ask...and could have a look in the attic of one of them...which if I canndig through the insulation might give some clues as to pipe route.

    Would it not be "normal" to route the hot into the attic space and drop down to the consumers.....rather than down to, I assume the floor, to be distributed?

    I think I will order an access panel and cut into the tank cupboard and see what I can see in terms of pipe routing I have an inspection camera which is about a meter long so will hopefully see a fair bit.

    David
     
  9. terrymac

    terrymac Screwfix Select

    Am I right in thinking the natural water level in the vent pipe will be the same as the water level in the CWT?

    David[/QUOTE]

    ******* Yes that's correct *****

    In an ideal pipe layout on a gravity hot water distribution set up , a continual fall from the take off at the top of the cylinder would be best practice. However taking pipe runs vertically to points higher than the top of the cylinder should work fine ,and sometimes have to be done this way ,for instance if your cylinder was sited on the ground floor ,and bathroom on first floor. So where can air enter your pipework ....... Vent pipe , cold water storage tank ( if the water level drops to such a low point that the outlets are not immersed ) a joint on the pipework where air can be sucked in ( exacerbated when a pump is present ,as in a power shower ) . By the way what temperature is your dhw heated to ?
     
    Last edited: Apr 19, 2018
  10. HomeAutomation

    HomeAutomation New Member

    The HTW temp measured around the neck/exit is 57 degrees or there abouts... hard to measure really... and I cant remember what the thermostat is set to on the tank, but will check. I did replace the tank thermostat 18 months ago to rule that variant out.

    The air issue seems to be the same if its heated by the boiler or by the immersion element... so I had kinds ruled out the tank temp - but it is a good call as 99% of heating cycles are via the boiler as you would expect.

    I did wonder if more head would help - not that I could increase the level of the CWT by anything more than 15" at a push - would that really add anything other than hassle?!?!

    I just wish I had been in the house at first fix so I could have seen the pipe runs... and slapped the guy for his choice of runs... hehe...

    David
     

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