AAV venting constantly venting when system is started.

[julesverne]

went to a house today. ideal classic with an unvented cylinder that is a y plan that has been converted to a sealed system.

problem is that when it is started the bottle vent which is situated just before the flow into the cylinder constantly vents along with red iron oxide when the system is started. now my first thought were the expansion vessel was faulty but this isn't the case no pressure increase when boiler is running. but on further inspection there is a lot of noise in the system/turbulence lot of old rads with valves showing streak mark of red iron oxide. so i suspect air is being drawn through microscopic holes. also top 2 rads in the attic do not warm up completely or not at all according to custard. system has a wilo gold60 pump could not check it's stats as they has rubbed off the top. also system doesn't seem to be losing pressure

i think this is a case a sludge in the system made worse with air being drawn in somewhere at some point. my thoughts would be to flush the system completly and put some sealer in and balance the system. i would have changed the valves but with the age of the radiators i dont think the rads would survive me taking them off and customer are old dears with not much money.

would you guys let me know if i am on the right track or should i be looking at something else that i have missed.

all replys great fully received.

 

[Dannypipe]

Well you've done the right thing and checked the usual suspect - the expansion vessle.

Could be sludge or could just be a broken AAV?

 

[WHPES]

If youve got red iron oxide then air or fresh water is getting in, or there is no inhibitor left, causing rapid corrosion of the system.

 

[diamondgas]

Just a thought 'julesverne', Could the pressure gauge be blocked/stuck? You may have no or very little pressure/water in the system. Could well be worthwhile checking that out if you haven't already. Just seems weird that the AAV only passes when the system is running, you'd thing if there was pressure behind it it'd be passing constantly if it's faulted?

 

[aggis]

Red oxide is active corrosion, send a sample to be tested, to say, Sentinel.
Correct analyst will help you on the correct course of action.

 

[julesverne]

been back today. changed the aav just to be on the side considering they cost a few quid and added some inhibitor and leak sealer as a temporary measure for the time being. system seems to be heavily corroded and customer is aware and appreacitaive of this so going to go through with them there options over the weekend. thanks to all for replying.

i only got gas safe registered last year but i think my fault finding logic seems to be on the right track but grateful to all for replies as it's nice to know other plumbers are willing to help with good advice