Constant airlock in hot-water plumbing?

Question

Hi all, this is my first post, so I am hoping someone can give me some good advise here. I live in an old house with a header tank in the loft and a hotwater cylinder in the kitchen on ground floor. The problem I am having at the moment is a re-ocurring hotwater loss. There seems to be airlock in the hotwater pipes. Cold water is always fine. I've had people in with professional pressure hoses from mains outside my house to try and flush it all out. But although it does work for a day or two the problem is back again. So far I've had this done 3 times in a period of about a month and a half.

This whole thing started, as the water company recently did work on pipes outside our house. They said all the pipes had to be replaced as they were old victorial pipes or something. While they were doing this work out on the street, somehow some dirt got flushed into out system, which went all the way to the loft tank and they came to flush it out. Ever since then I've been having this issue.

Answer 1

Your problem could stem from several different factors,but the basic one is your pipework from the storage tank to the cylinder which should be of 28mm diameter,anything less will not produce a balanced flow of water via a sufficient head of water ie.the height between the storage tank in the loft and the entry point of the cold flow supply on the bottom-side of the cylinder.Secondly the draw-off/vent pipe from the top of the cylinder should be one size smaller than the cold feed pipe to the bottom of the cylinder ie.22mm,as this supplies your taps also it should stay as 22mm untill it is branched off to 15mm for tap supply only, 22mm for the bath taps,this pipe work also should continue to rise into the roof space and bend back over the storage tank at a sufficient height above the cold water line of the tank thus leaving an open circuit which allows for expansion of the hotwater system.YOU HAVE TO CHECK THAT THIS VENT IS NOT BLOCKED as i think your air lock could be caused by the inability of your hotwater circuit not being able to vent out any air that is drawn into the system when you relieve the pressure upon opening a tap.Also a dip in the pipe work could trap this air in which case it would have to be repaired especially true if that crap plastic pipe was used[not clipped],But you could force the mains water up the hot water system via the tap using a hose pipe. {watch for the spray,wrap a cloth round and hold tight,an assistant is a must} listen for it clearing up through the connection at the bottom of the storage tank in a big gurrgle,this type of airlock can also be caused by drawing off hot water at more than one scource at a time ie;all hot taps in use at the same time.

Answer 2

From your description it would seem that you are not getting water into the cold storage tank (Header tank normally refers to a CH system) OR it is nor getting from there to the cylinder and taps. First step is to run the hot taps and look into the storage tank to see if it is filling quickly enough, or is the level dropping? If this is ok, is the water leaving the tank quickly enough to supply the taps? The results of this quick test may indicate a blockage somewhere, possibly you have sucked in some debris following the repairs. You may also have a blocked filter somewhere on the mains supply pipe, at the water meter, or pressure reducing valve if you have them??

Answer 3

I had a similar problem with a persistent air lock. I got a gravity fed system with a tank in the loft that feeds the hot water cylinder. The air lock issue reoccurs every week or every two weeks. I have to feed the hot water with cold water by bridging the cold with the hot water which forces the air out but temporarily solves the problem. All that changed when I noted that the pressure gauge off the compression tank was dropping and not in green zone on the gauge. I used a bicycle pump to pump the bottom of the compression tank and re pressured the tank. The needle dropped so I pumped until the needle stabilised on the green zone. This took about 2 days of monitoring. Eventually the needle remained on the green zone. I am now experiencing better flow rate and hot water pressure, and no spluttering or water mixed with air out the pipes. I will keep an eye on this. This may not solve your issue so would always recommend a qualified plumber to check out your system.

Answer 4

24

Answer 5

size and distance is a issue .the tanks may need to be drained and temperatures set higher .worst case scenario replace the tanks or parts on them. whole tank replacement in the long run can be a wiser choice for the cost of repair .depends how old the tank are . and locations .

Answer 6

YOU WILL HAVE TO EMPTY TANK--
MAKE SURE ALL WATER LINES ARE OFF. REFILL.
AFTER FILLING TURN ON ALL LINES AND LET AIR FLUSH FROM TANK THRU ALL LINES.