Greetings plumbfolk I'm on a bleeder gizmo hunt

[beachkat]

so the challenge is to come up with an automated inline gizmo for purging air which is regularly getting into the outlet pipes running from 2 vented coffin tanks. These supply a pair of flats below a new 2nd floor roof conversion.

BACKGROUND INFO... the copper pipes were neatly laid by an experienced and trusted plumber and (seemingly) regularly clipped / supported along 4mtr straight runs along the eaves before elbowing inward and down thru the subfloor to supply the hw cisterns in the flats below. We don't think they're sagging but maybe the runs were just a bit too long, who knows where the problem lies because...
the pipework is now well and truly buried within 30cms of acoustic insulation, fire barriers etc plus boarded & carpeted over. i.e we can't get to anything without destroying a lot of hard work. Sods Law the airlocks started happening after we finished everything so now the hunt is on ....

all replies most gratefully received, cheers James

 

[diamondgas]

What you done so far to try and remedy, beachkat? oh! & welcome to the forum

 

[markfxy]

why not raise the tanks by putting 18mm ply under neath them

 

[beachkat]

thanks.

yeah it did occur to me raising them up a bit but access is really limited around them i.e jammed up against the eaves. one flat (directly below) clears easily by using vacuum on CW supply but the other (2 floors down) is a pain. on that one we're connecting mains to hot water circuit and hoping to blast the air backwards into the roof tank. Both temporary solutions tho' and what we need is a permanent automated one. Also considering maybe installing electric inline pumps between downpipe and cistern CW inlet?
One possible explanation for these airlocks might be a drop in mains pressure - local water company has been doing major works in the area for past 12 months but they wouldn't confirm (or deny) that they'd lowered the pressure when we called them. grr

 

[kay-jay]

if the the hw is tank fed and you can purge the air by blasting mains through system and then it is getting airlocks again it would suggest to me that there is air being drawn in from somewhere. i would be looking at any visible pipework connections compression etc. before ripping things apart. i would also check there is adequate clearance of overflow/warning pipe above water level.

also how would a drop in pressure affect air getting in the system? seeing as it is tank fed i would have thought any bubbles from supply would settle before draw off! also this can be checked by simply observing the water as it refills the tank after a draw off.

how would fitting a pump help??
surely if you are drawing in air from somewhere a pump is only going to do it more efficiently.


imho


KJ

 

[EPH]

So do you think they're running dry and that's where the air is being introduced? Are they linked together or does each tank supply each flat?

If so is it possible to link the tanks so both flats have twice the draw and unlikely to be using water at the same time so less likely to be emptied?

 

[beachkat]

thanks for your replies. some answers...

There's been much headbanging about the prob so some of our own 'theories'/'solutions' are most likely wild rubbish (please forgive). e.g
speculating that fluctuating pressure may be causing lowered tank levels or allowing dirt/particles in causing blockages. Tanks can't be linked as they're separate flats. Certainly the plumbing in both flats below ain't gd and we're checking for obvious air ingestion. But worth considering that neither had probs before the roof conversion and now BOTH do, so this is a problem that's common to both taking us back to the pipe runs. As for pumps - theory was it would help draw air down to where it could be bled off easily - another wild idea I guess ^^

pix before and after relocation

 

[kay-jay]

normally i'd consider linking them or changing for 1 larger combined tank but only as a last resort, the air has to be coming from somewhere....but it seems strange that both flats have this problem when they are on seperate/unlinked tanks!

how does the new tanks connect to the existing pipework? compression or soldered? check all nuts etc...

bit of a head scratcher!




KJ

 

[beachkat]

not sure how new links to old, will check with guy who did it - educated guess would def be soldered. Yep major headscratcher - you're not wrong there!! :thinking:

we're thinking along the lines that at some point along the run both sets of pipes are maybe levelling out enough to periodically idle the flow OR hitting a bend in a way that causes bubbling if that's possible? Airlocks seem to occur every few weeks.

Kinda leaning towards trying the raising-tanks-up-20mm idea to increase fall but still hoping u bright sparks here will come up with more suggestions.

thanks again.

 

[kay-jay]

raising them will only do the same as fitting a pump which is to draw the air in quicker and more effectively. as for creating bubbles from hitting bends i don't think that would be possible unless there is a pinhole leak on the solder and as the water passes through air could then be drawn in, however with both tanks doing this it would be some coincidence.

i would definately look for any signs of bubbles in the cisterns while they refill after someone draws water off in the flats, is it possible that the turbulence in the cistern water as it refills during draw off coupled with a vortex created at the outlet during drawoff is enough to draw air down from the surface??? i think this would explain why the upper flat doesn't suffer as much as the lower flats because less head = less draw in of the air. if there ain't any bubbles passing from top to bottom and the overflows have clearance above water level then it has to be downstream of the tanks but then we're back to the coincidence thing


KJ