Constant Airlocks

[Plamber]

Hello all.

The system is an open vented system with the cold water tank 5" above the cylinder in a small cupboard so there is no way of removing them (must have been built in). it is heated by immersion heater.

The thing is, its airlocking every couple of days, the woman said its been like that for 8 years and has only now tried to get it sorted.

What i have tried so far is emptying both tank and cylender and filling up from washing machine valves, from bath taps, WHB taps and kitchen taps. getting everything working for a few days then the pressure on the hot water drops to very slow. the kitchen and bathroom are on different sides of the flat and all the pipework seems undamaged (no kinks,dents). I even had another and very experienced plumber with me today and he was confused with it. his suggestion was some kind of flange, something ive never fitted or used before.
ADVICE PLEASE.

thanks in advance


I have also increased the hight of the vent pipe as much as possible.

 

[macplumb]

Dose the hot water distrabution pipe rise slightly when it leaves the cylinder?

 

[Plamber]

slightly yes, not more than 2 inch though.

 

[macplumb]

Is there a pump on the system for a shower or to increase flow?

 

[Plamber]

no, its a very basic system. flat doesnt even have a shower.

 

[Plamber]

BUMP

Just bringing bck to top

 

[secret squirrel]

Hello Plamber,

I've been following this post but I haven't got any useful to contribute but I don't understand your last post.

I don't understand why the customer wants something doing now after such a long time, has it got worse for the customer!

Is it possible (I really don't know) that there is a dodgy gate valve somewhere creating a problem or a tap, as I'm typing this I'm thinking 'you'd see a leak though"

 

[Plamber]

She lives in a rented flat from a housing association. the previous owners ignored her when she mentioned it. but the housing association i work with have now purchased the whole housing scheme and pride themselves on prompt repairs.

The only thing i can currently think of is fitting an unvented cylinder. but that seems pretty excessive. is there some kind of flange or fitting i dont know about that i could fit to the vent pipe??

 

[secret squirrel]

I can't think of anything, hopefully, someone else will. Have you spoken to your local merchant about fittings etc. I find them extremley helpful.

 

[moony]

not sure really does the cwsc fill up quickly enough ? no blockage? maybe when filling the bath its emptying quicker than filling the cylinder,

an unvented ? why not a combi ?

 

[Plamber]

the cold water tank is massive and definatly has enough water in it.

Its an open vented system, no combi due to the block not having gas. its electric heating they have.

know abput any kind of fitting i could fit to the vent pipe to stop it drawing in air.

 

[WHPES]

If it is the rate of fill of the cistern, you could change the ballcock to a 3/4" one.

 

[Puddle]

When you leave after back filling all pipework full of water and running nicely,so air is getting in from that point,as said tank may be big enough but what about refill,she is in flat ,does tank feed other flats as well causing to empty
Is supply pipework to cylinder from tank to her flat only or feed others,if so could be another flat could be robbing her supply
Also could vent pipe be blocked up,check clear
Presume when you back fill pipework you let run for 5 mins or so
Does she take baths,if so ask her to fill slower and see if then ok

 

[Plamber]

i've filled a few baths after back filling the system each time ive done it. and then the pressure is fine for a few days, one time i did it it was fine for 2 weeks!

As for the tank, each flat has their own one and this one is definatly big enough for her and fills up fast enough. there is no shower in the property.

 

[moony]

there a valve that can be fitted to the vent to allow air out but not back in? im sure ive heard of this but i cant recall ever seeing one. maybe it would help. non return air valve - not sure on the legallities of fitting one of these to the vent - would be pretty dangerous if it failed.

 

[Plamber]

my plumbing merchant doesnt seem to know about a fitting like that, although he doesnt know muchb to be honest. would it help if i tee'd in an other vent pipe firther down the hot pipe?

Also mybe some kind of flange fitting on the hot pipe just after the cylender? is there a fitting/flange that would help?

 

[payney1974]

Can you trace the hot pipe from the cylinder to all the outlets? Is it all surface as its a flat or does it go under floor? If under floor i would think there could be an airlock on poorly installed pipework?

 

[Plamber]

the pipework goes under the floor, its pretty obvious where everything is. goes down to a tee and slits left to the bathroom and right to the kitchen. but after i clear the airlock its fine for a few days to a week.

funny thing is, all hot water in the flat gets affected not just one side. could the be a blockage somewhere? i had a very experienced plumber with me one day and he was just a confused as me. he seemed sure that there wasnt a blockage.

 

[wards]

maybe a silly idea,but is the thermostat on the immersion heater set too high?could just be overheating and subsequently blowing off into header tank thus allowing air to be drawn into the system?just a thought
si

 

[Plamber]

thats something ive not checked actually, thanks wards. ill give that a try when im back next, its a long shot though.

water doesnt seem too hot though. would bubling water from the vent pipe pull in air??

 

[wards]

you have answered your own question.HTH
SI

 

[TerryH]

You should not impede the vent pipe. It should always be open.

What size is the vent; 15mm or 22mm.? I've recently come across two which were 15mm. One was my own job and I changed it to 22mm. The other was helping a mate, he left it with the intention of returning to change it after we had replaced the hwc.
He was called back due to hw flow diminishing to nothing. I suggested we change the vent to 22mm and it's ok now.
I think as the taps opened air was drawn back down the vent, past the hw take off and emptying the pipe; flow, slow flow and then no flow. The larger diameter pipe allows water to flow easily without restriction and draw down of air.

 

[Plamber]

vent pipe is 22mm. and so is every one on the housing scheme. there is about 50 flats all with the same system. if replacing the thermostat failes il see if its possible to up the pipes to 28mm from the cylinder

 

[charlie frederi]

Hello all.

The system is an open vented system with the cold water tank 5" above the cylinder in a small cupboard so there is no way of removing them (must have been built in). it is heated by immersion heater.

The thing is, its airlocking every couple of days, the woman said its been like that for 8 years and has only now tried to get it sorted.

What i have tried so far is emptying both tank and cylender and filling up from washing machine valves, from bath taps, WHB taps and kitchen taps. getting everything working for a few days then the pressure on the hot water drops to very slow. the kitchen and bathroom are on different sides of the flat and all the pipework seems undamaged (no kinks,dents). I even had another and very experienced plumber with me today and he was confused with it. his suggestion was some kind of flange, something ive never fitted or used before.
ADVICE PLEASE.

thanks in advance


I have also increased the hight of the vent pipe as much as possible.

Hi
have you tried servicing the ballvalve
or shut the cold feed to the cylinder and drain the head off
once the vent is clear of wateropen the cold fill also is the element switching off at 60 degrees ie not boiling over filling the vent with water causing air lock
or it could be there is not enough gravity to supplie areas dependent on position of taps and pipe sizes.