Air in system. Help please

[NDUD1]

I have replaced my bathroom but I cant get rid of the air in the system. I have back fed it with the cold tap so many times I have also bled all the rads. I can hear the air bubbling back into the cylinder. but when I run the hot tap afterwards it only lasts about 5 mins max. have been backfeeding on and off for the last 3 days but its no better. There are no leaks in the plumbing work that I have done but there is a small leak coming from the mains stopcock. could this be the cause. Any help or advice would be greatly appreciated.

regards NDUD1

 

[secret squirrel]

I am presuming that you have a system boiler and the cylinder your refering to is the hot water cylinder.

If you've back filled the system and you didn't empty the cylinder you may have a blockage in one of the pipes.

I had this problem replacing a cold water tank. Could hear gurgling (air) tap would run for 5 minutes then stop. Then gurgle again, then run again for 5 minutes.

I took the it apart from the isolator and checked the flow into a bucket. There was poor flow so had a rough idea where to start looking.

Have you altered pipe work, changed where and how it runs? I think we'll need a little more info.

Slight leak from the stopcock should not cause this problem.

 

[NDUD1]

Hi

some pipework was going above skirting so changed it so it goes underneath. I have also put the bath at the end of the run as opposed to the start but nothing apart from that. the main run is 15mm pipe the original run to the bath was 22mm it is now 15mm...im thinking this could be the problem...do you agree

Regards NDUD1

 

[secret squirrel]

If the pipe work runs underneath other pipe work you have created a trap and will be a nightmare, if you've put in loads of elbows and bends this also restricts flow so again will be problematic, if you've further reduced the pipework form 22 to 15 you've again restricted the flow.....

I don't think I've helped really, but its difficult only going on description..

 

[NDUD1]

If the pipe work runs underneath other pipe work you have created a trap and will be a nightmare, if you've put in loads of elbows and bends this also restricts flow so again will be problematic, if you've further reduced the pipework form 22 to 15 you've again restricted the flow.....

I don't think I've helped really, but its difficult only going on description..

Thank you...

I think you have hit the nail on the head, I have put bends in to hide the pipe work but wouldnt think this would create an air lock. or is this created when the flow of water stops....

Thanks again

 

[secret squirrel]

I thinks its a combination, water builds up forces its way through then dies as its in a trap with no flow

 

[NDUD1]

does it also have effect with the cold water feed. as I have put bends in to hide that pipework as well. although there are no problems with the cold water taps.

Regards

 

[GreenArmy]

Did you drain down the hot water when you replaced the bathroom (turn off stop-cock and open all hot taps)? If so, have you checked the ball-valve in the loft tank to make sure its re-filling OK? If not it could be that you are draining off the water quicker than the tank can re-fill.

 

[jpm]

pics of the pipes to the DHW cylinder please could be a primatic/annulous

 

[justlead1]

Hi. When you say "back filled from, cold tap" the tap you back fill from needs to be mains feed. Is that the case?

 

[Puddle]

persume you have checked the ball valve supplying the tank is filling correctly

 

[NDUD1]

yes the cold tap is mains feed. i'm thinking theres too many bends and elbows in the pipework as i've rerouted it under the floorboards. restricting the flow.

thanks for reply

 

[justlead1]

Hi. Is the hot on the kitchen sink ok? Although elbows and smaller dia pipe increase frictional loss, you should still get an uninterrupted supply when air is extinguished. As has been said check cold water storage cistern for water and that the gate valve that may be on the cold feed to the cylinder is fully open as is badly restricted air will be pulled down the vent when hot tap is turned on.