Hot water pressure / air in system

[Fix-it-duck]

My upstairs hot taps are causing me serious grief. I moved in about a month or so ago so don't know what changes were made to cause the problem and how long it has been going on.

The water runs normally for a second or two then it reduces to a trickle, this goes on for about 20-30 seconds, then it begins to splutter a bit, some bubbling can be heard elsewhere in the system (I've traced this to air pouring out of the vent above the cylinder). Then the water flies out at top whack for a couple of seconds, slows down, splutters etc, etc. This happens whether the water is hot or cold.

Now to the pie runs. the hot water tees off the vent pipe a couple of inches above the cylinder. It then runs horizontally for a few inches and goes back up again and into the loft. It weaves around in the loft and the shower tees off (this also has the problem) it then goes down into the bathroom and to the taps. My initial thoughts were that we had a huge air bubble in the pipe above where it teed off the vent, so I blasted it with mains a few times. this did not change a thing. I'm now wondering if the water is sucking air back down the vent pipe in a capillary action.

I'd be grateful for any ideas or suggestions and diagnostic thoughts or solutions

Thanks,
Fix-it-duck

 

[masona]

Make sure the ballcock in your cold water storage is okay,possibly the ballcock got struck and when the water tank empty,air got in creating a airlock.You need to get a water main pressure back up to the hot tap with a hose somehow and force the air out into the tank.If it a bath/shower mixer,I have made a connection on the shower pipe outlet with a garden hose & turn the shower lever to shower position and open up the hot tap with the cold tap shut and turn on the water main on.This way you don't get wet !! Don't do it for too long as the water level will overfill out the overflow.

 

[Fix-it-duck]

thanks for the tips. I've checked both of these though. The ball cock is fine now but that's not to say that it hasn't run dry before causing an airlock.

I tried removing the airlock using mains pressure a few times by connecting the mains pressure outside tap to the hot tap in the bathroom sink and openning them both up full. Didn't make a bit of difference. it started up gushing out and then after maybe 4 seconds we were back to the trickle again.

I'm wondering whether I need to fit a drain cock to the top of the hot pipe run to drain out an airlock or whether a one way vavle on the vent pipe could be the answer to stop air being sucked back down into the hot water.

It does seem to be releasing air sporadically(the knocking and venting) only to get another airlock when it begins to flow again

any other thoughts? (I'll try anything within reason!!)

 

[masona]

Try and do it a bit longer (sometime its can take longer to do),if not tie up the ballcock to stop water flowing into the water tank & get someone to turn the taps on to drain your water level from your water storage tank to approx half way,then somehow if you can get a garden hose and put it inside the feed pipe at the bottom of the storage tank (22mm copper pipe) and put some rags round it to stop the water escaping back inside the tank and open up the hot taps that causing problems also open up the shower hot side then turn on the water mains on which should blast out air out of your taps.Don't forget your swimming trunk!

 

[Fix-it-duck]

Cheers for the advice

 

[Fix-it-duck]

I see where you're coming from here.

I have drained the tank too but I let the water back in slowly. I could try this method again but with mains pressure by draining the tank and half the cylinder as you say and then shoving the garden hose down the inflow to the cylinder. That way I shouldn't need the trunks and rags!

Will keep you posted.
Thanks for the help.
Duck