air trapped in cold feed to immersion tank

[goateater]

hi folks
been having a problem with my hot water flow for many months
there just is hardly any pressure
after a few checks (and suggestions from various web sites) I thought the problem was a blockage in the top of the immersion tank, but the top outlet and the heater element are stuck fast in the tank, so I can't look into the tank
yesterday I had a bit of a play, turned off the cold feed to immersion tank
turn on hot tank (drained a little of the hot water)
turned on the cold water feed and I can hear what sounds like water running though air (space) as it fills tank back up
it sounds as if there is air trapped in the pipe that comes from the cold water tank down to the stop tap on the pipe that feeds into the immersion tank
I've disconnected the pipe from the immersion tank side of the stop tap then turned stop tap on, which let water flow into a super size builders buckets (drained out around 10 -15 gals, yes hear some air forced out.
reconnected pipe work, but its still about the same
the pipe run from the cold water tank to the stop tap I used is only 2 mts max
any thing else I can do

 

[Armo74]

Do all hot taps have the same problem?

 

[goateater]

yes same problem on all hot taps
as I said been on various web sites and having tested using info for forums tracked it back to immersion (& its input side)
thought before I go out and buy a new immersion tank, I'd do a few more checks
that where I found that by turning stop tap cold feed to immersion off
running hot water off, then turning stop tap on, as water fills up immersion, you can hear the water is trickling into the immersion tank, so think its air trapped, there are 4 bends in the pipework running from cold water tank to immersion, its only 2 mt run of pipe at the most

 

[Armo74]

Check level in CWSC.
Could be gate valve on cold feed slightly closed.
Could be scale in bottom of tank.
If you have a mixer tap try turning the hot tap on with your hand over the spout and then turn the cold on this should force the air back up to your CWSC.

 

[gigz]

Agree with above but if that fails drain down completely and loosen the compression nut on the top of the cylinder, check its clear. Went to a very similar thing few months ago and whoever had fitted the cylinder had just hacked away at the foam jacket and all the bits went inside, they also used the same female iron without cleaning the limescale out. This went on fir months, took about half an hour to fix it.

 

[goateater]

water level in CWSC is ok
gate valve full open (I changed the valve at the start of this week think that may be a problem)
tank is ok
I blow back cold water though pipes by connecting washing machine hose from cold pipe to hot pipe (taking end from washer and put on hot water pipe connection

 

[gigz]

Do you ever get any debris out of the taps ?

 

[Madrab]

Is there a rise in the distribution pipe work from the cold cistern before it drops to the cylinder?

 

[goateater]

there has never been any debris from the taps
there is no rise from the cistern to the cylinder
I live in a dormer bungalow
about a year ago I re-routed the hot water pipes, which are below the bottom of the hot water cylinder, at the same time I replaced the stop cock feed from the cistern to the cylinder, so the cold water cistern
since that time I've had what I call lower pressure from the hot water pipes
I have thought about replacing the 22mm cold water feed pipe with a 28 mm feed pipe

 

[Armo74]

When you say you replaced the stop cock do you mean a red wheeled valve or a mains stopcock?

 

[goateater]

when I say stop cock I meant the gate valve fitted between the cold water cistern and the hot water cylinder (immersion heater)

 

[Nige F]

replace the gate valve with a Full flow Ball isolator valve

 

[goateater]

how will replacing the gate valve with a ball valve get the trapped air out
there are no drops of water leaking so air is not getting in,

 

[gigz]

Get back to basics, when you say immersion tank do you mean a copper cylinder with an immersion heater fitted ? If you persevere you should be able to unscrew the top connection (forget about unscrewing the immersion) on the cylinder, you may need to heat it up and be carefully not to distort the cylinder. Check in the cylinder and the pipe that comes off it. Pics are always useful if you can.

 

[goateater]

yes wen I say immersion I mean the copper cylinder
I can undo the nut on the hot water out put side (top of cylinder) but the copper pipe end that goes into the cylinder is stuck fast, I've used wd40, hit it, just will not move
worried that I could bend the cylinder or bend the copper pipe if I carry on
thought about cutting the pipe and hoping that then I could twist pipe out
but now i'm thinking that the probelm is air trapped in the feed to the cylinder, its only a small length of pipe 2mts or less but it has 4 bends