Air in hot water pipe for kitchen - bungalow property

i have a gravity fed CH system in a bungalow.
The hot water tank is behind the bathroom and cold water in the loft, ( above the bathroom )
The hot water in the bathroom is fine, no air appears at all
On the longer run to the front of the property where the kitchen is and cloak room after a few days air appears and taps start to trickle air,

i was advised to put an auto air vent mid way in the pipe due to the length of the run but im just seeking advise from the pro`s on here as to whether that is right ?

 

Do you mean gravity fed hot water - as in tank and cylinder? I had a similar problem once, and it was a combination tank and cylinder which had fallen to one side. I’d be checking the tank is filling correctly and checking the pipe itself to make sure it’s not falling back, trapping air.

 

Yes hot water cylinder, tank was new 18 months ago, bathroom is fine,

 

Again, look along the pipe length for any rise in the pipe, also there could be a restriction/blockage.

 

Already checked, the pipe hasn’t much fall to be honest but is almost as long as the property, when the air is there it’s easily resolved with putting a wet a cover the tap and drawing it out, it then appears a week or so later

 

Does the hot water pipe to kitchen run through the loft ?

 

yes through the loft

 

Is the branch pipe that heads to kitchen ,taken from the vent pipe ? Pics of your plumbing / pipework may be helpful relating to the kitchen pipe .

 

ill check this but dont think so
the run to the kitchen does t off towards the end to feed the cloakroom

 

It's the origin of the branch pipe that's in question. Where does the branch that heads toward the other end of the property actually connect to the cylinders distribution pipe ?

 

So I went in the loft today to see how things are working, the bathroom hot water pulls from different pipes that look to be connected to the CH and off of a pipe that has a vent
The kitchen pulls from what looks like the pipe from the top of the cylinder and there is no vent on any run of this pipe, it’s a 22mm pipe that reduces down

 

The pipe that runs from the top of the hot water cylinder should be feeding all your hot water outlets. That pipe should rise upwards to the cold water storage cistern (CWSC) in the loft, it then loops over the top and points into the CWSC (the open vent). The hot water distribution pipe should tee off of that vent pipe before that pipe gets to the CWSC and out to supply all the hot water outlets.

If you kitchen is being supplied by a pipe from the top of the cylinder but that pipe does not rise up to the CWSC then that's your issue, air bubbles from the heated water is being caught in that pipe.

I'm not exactly sure where your bathroom is being supplied from if it's not the same pipe that feeds the kitchen unless the HW cylinder has a separate tapping for a secondary supply from the side of the cylinder. If it is then it is being used as the expansion but not as the vent.

As @terryplumb mentions , a few pics would say a thousand words and give us a better idea of what's going on.

 

You might need to check that you don’t have this situation as well

 

No this is not the case

 

Photos will help better then.