Losing water from F & E Expansion Tank

Hi all what a great Forum Site.

System is 8 years old

Over passed two months I have had to top up the F & E Expansion Tank ( weekly ) by 2.5 ltrs of water to maintain correct level.

Yesterday I called out Support Engineer for Repair/Advise.  

Following an Internal/External inspection of our unit I was subsequently advised that our Systemate 2000 had no visible signs of External water leakage and therefore any leak must be internal to the Thermal Store/Coil.  I was further advised to add Fernox F4 Heating Leak Sealer to the Thermal Store via the F & E Vent Pipe. Hopefully to seal any internal leakage.

Could anyone please advise if this is accepted practice & or whether any damage could be done to Thermal Store before I carry out this option.

Many thanks in advance

Delboy_Lee

Hi Lee
As your Systemate 2000 ( not an Boilermate2000)is part sealed ( the coils to your boiler and to your radiators are pressurised) the cylinder himself, is of course open vented.
If there would be a leak in the internal coils, your F & E tank would of course over flow, not going empty. But the Cylinder water has to disappear somewhere, as you have to top up regularly. May coursed from some leaking Pump valves or leaking washer on some joints .They are sometimes hard to spot.
Yes leak sealer would be the first and obvious action, but, just tip the sealer in to the F&E, not in the vent pipe. Give this about 10 days to get in to action and wait watt's happen.
Also the water in this tank (F&E) will slowly evaporate, and has to be toped up about every 3 month. Specially if this cupboard is also used for storage ( old blankets, towels ect) and mostly the doors are not vented so this is quiet hot in this cupboard . Also do not overfill the F&E tank ( max half way up), this also coursed faster evaporation as well.
Hope this helps regards
Mario at Mario's Boiler Service

Hi Mario

Thanks for your speedy reply and comments, these are very much appreciated. As you can tell I am not a plumbing or heating expert and any help is welcome to resolving my current problem.  It is interesting that you refer to evaporation from the F&E tank which I have noted. Thank you also for confirming my concerns with regards to using the vent pipe to put the sealer in? I will do as you have advised use the F&E tank, will one 500ml bottle be sufficient for this purpose?

You can be assured that I am very aware of the safety aspects ( Fire Hazards ) of the Airing Cupboard & have no blankets etc stored or kept within.

Having seen some awful photos of water damaged Thermal Stores I make a habit to remove the Front Cover approximately every 3 months to check for water leaks etc,  so was taken by surprise when I found the F&E tank was suddenly losing water & no obvious visible outlet .  For the passed 5 years the F&E tank has been checked for correct water level prior to the BG annual service and ( No ) top up has been required until as stated earlier few weeks ago.  Perhaps like me the system is getting a bit old in the tooth now and just needs some Tender Loving Care ( TLC ).

Will get some Fernox F4 and report back on any changes in the next couple of weeks ? hopefully with some positive results.

Thanks again

delboy-lee