Greetings plumbfolk I'm on a bleeder gizmo hunt

[BLOD]

So do you think they're running dry and that's where the air is being introduced?

I'm with EPH on this one

How much water do the new tanks hold compared to the old ones ?

 

[beachkat]

thx KJ, interesting & appreciated.

new ones 25 gal coffin and old look like 30 gal round (see photo in post#7) so should we try decrease/increase tank water levels? or maybe raise vent pipes higher?

 

[BLOD]

try running a bath tap ,while watching the water level in the tank - see if the tank goes anywhere near empty after a while.

 

[turnpin]

Hello Beachkat and welcome to the forums I think personaly you have undersized tanks causing your problems BS6700 recommends that you need 115 ltrs for both hot and cold supplies i.e230 ltrs total although its hard to determine the size of the tanks you removed It looks to me that they are a lot bigger than the new ones . Also the pressure on the incoming main filling the tanks may not be as good if both tanks are calling at the same time especially when both flats are drawing water at the same time causing the tanks to empty quicker.Good luck and please let us know how you get on regards turnpin

 

[kay-jay]

thx KJ, interesting & appreciated.

new ones 25 gal coffin and old look like 30 gal round (see photo in post#7) so should we try decrease/increase tank water levels? or maybe raise vent pipes higher?

first thing is to see if the tanks run dry during draw off and get air in that way. while watching the tanks during draw off watch for air bubbles travelling from the filling 'splash' travelling to the outlets i'm sure it has to be one of the two.

the coffin tanks should have enough capacity for hot water (is the cold in the flats mains fed?) but they are not tall/deep which means with increased draw from the head on lower flats there is more likely a possibility of bubbles being drawn down as said above. if this is the case position the feed at opposite side of tank to outlet then any bubbles would have to travel further ie across as well as down and should sort it. obviously if they are running dry then you will need bigger tanks

KJ

 

[beachkat]

aha turnpin, blod & KJ think you've all cracked it - insufficient head and tanks periodically running too low.

that would explain a lot e.g.
intermittent nature of airlocks,
lower flat being worse than higher one - 1st floor never uses bath (infirm), ground floor does regularly. PS: feed is already well away from outlet vortex (1.4m)

now have to work out how to increase capacity in limited space. joy

will keep you updated and thanks again

 

[tackleburger]

I would check the ballvalves are refilling at full pelt strip down and check for grit in the valve seat causing the tank to run dry this is a common problem after the water company have been working in the area. Even try and fit a fluidmaster fast fill valve side entry.

 

[beachkat]

Thanks for input. Can't get back in there just yet for doublechecking but last week ballvalve flow looked fine, clean condition (pretty new) & smooth operation plus tanks have been flushed thru a couple of times - no trace of unusual/lingering sediment if it was there. Next step is close watching flow during max draw-off (as advised) and discussing FF valve. more I think about it, insufficient head does seem to tick a lotta boxes.

 

[beachkat]

Postscript. closely checked operation of tanks and fitted Fluidmaster valves (restrictors removed) - so far no probs.

If airlocks do reoccur (and since it's a major operation to squeeze larger tanks in) we figure we can get round it by connecting all bathroom CW to mains and leave roof tanks just for supplying hot cisterns.

 

[stevetheplumber]

Postscript. closely checked operation of tanks and fitted Fluidmaster valves (restrictors removed) - so far no probs.

If airlocks do reoccur (and since it's a major operation to squeeze larger tanks in) we figure we can get round it by connecting all bathroom CW to mains and leave roof tanks just for supplying hot cisterns.

this could cause more problems than youve got if there are mixers or showers