Blockage inside 15 y/o Boiler ?!?

jmkennedyie

Has anyone heard of a 15 year old boiler becoming blocked internally?

I have been 5 years in my house and anytime me or plumber doing any work on the system it has always been dodgy recommissioning the system.

Last straw was last Wednesday when hot water from oil boiler would not reach the house. So I started to investigate.

Added various drain valves on flow and return at the boiler and some stop cocks and finally forced mains in various places to try and clear suspected blockage or airlock in under the house, but water flowed out the return fine. So no blockage between boiler and house on flow or return.

So only other place for blockage is inside the boiler itself. Took off pump. Forced mains in the boiler return, and nothing came out the boiler flow at the pump fitting. Not a drop. Yes pump valve was open and mains tap and hose were not frozen.

I couldn't believe it, and no plumbers I've spoken to can believe it either. Grant have seen boilers clogging up eventually, but never one only 15 year/old.

Has anyone come across similar? It's a 15 year old Grant outdoor 50/90.

System has always been problematic, but gunged up occassionally blocking boiler would explain all symptoms. Grant told me no valve inside the boiler.

Water in f&e tank is a bit dirty, but not gunge, it was still consistency of water.

Had plumber over today and initially could drain top of boiler, but then it stopped. Wouldn't refill through the return (in my opinion due to internal blockage). But later either coz of some steam we created inside the boiler, or running both boiler pumps at same time, I believe the blockage was freed up and the heating has been working perfectly since.

So unfortunately I didn't have time to prove the blockage to the plumber. He will look into it more when weather better, and do some other jobs for me, but if anyone has come across similar blockage or can think of other explanation would be very grateful!!!

ntpm

I have come across heating systems/boilers around 25,30 and nearly 40 years old that have been very dirty/gritty. Never come across totally blocked boilers.

Blockages are generaly due to corrosion etc. This may be due to exessive air being introduced in to the system... do you have solid fuel heating. Is the hot water pitching (flowing up the (OSV) vent pipe in to the attic).

I have however come across newer boilers that have blocked up heatexchangers... I put this down to poorly designed/ installed systems, no flushing and lack of inhibitor.
Lets see what the Celtic Tiger/ Building Boom has left for us in the next 10 years...

aujopimur

Thats what happens when inhibitor is not used

yoshytoshy

Some boilers have a flap ,to prevent reverse circulation.
But your plumber would know about this.

jmkennedyie

thanks for all responses. I forgot to mention yes there is a Grant back boiler on the system, as well as the oil boiler.

Corrosion sounds like a real possiblity now that you mention it. I have not put inhibitor in it, not sure about previous owners but I very much doubt it. Problems already existed when I bought it 5 years ago.

House was rented for 10 years before I bought it. Doubt chimney ever cleaned based on what I found behind back boiler grill, so standard of maintanence low. Tenants may not have known to switch on back boiler pump, i fact I think pump was bust, and I know that in this case and fire on yes hot water does get into tank. So maybe this happenned regularly for 10 years. If I am hearing you right sounds like this introduces air into system and accelerates corrision. Ouch. Don't fancy having to replace back boiler.

Grant didn't mention a flap, but whether it is there or not a moving pile of corrosion stacked up inside the oil boiler could totally explain blockages in there.

I'll guess I'll do a total system clean / mains flush of boiler on its own & mains flush of total system, see what comes out, and refill with inhibitor.

I know total powerflush is an option. I wonder would it flush a hole in my back boiler :eek: