Feed and expansion tank line possible blockage

[JandS]

Hello,

We have an open vented central heating system (think this is the correct term). A couple of weeks ago our boiler (Baxi Solo 2PF) started making a loud gurgling/boiling noise as did the adjacent radiator. We switched off the boiler and later our plumber discovered that the circuit board on the boiler had burnt itself out (evident by a large charred area!) and replaced the board. The boiler subsequently worked fine but half the radiators in the house would not warm, and the pump made noticeable whooshing noises. Suspecting air we tried to bleed the radiators and were partially successful but some radiators would not bleed (we opened the bleed and neither air or water came out and in one case we think one radiator was sucking in air!).

Our plumber thought at the time that the line from the feed and expansion tank was blocked and that the system wasn't refilling (the ball cock valve works fine - you can push it down and get fresh water to enter the tank). Judging by the large amount of crud in the tank this seems a reasonable assumption.

We hoped at the time we had a small blockage and that our central heating system would slowly refill (with frequent bleeding of radiators), but this didn't work and the boiler eventually tripped out on overheat.

We tried draining the cental heating system to encourage it to refill from the expansion tank but this hasn't worked.

A plumber is coming round tomorrow. He is suggesting connecting mains water to the expansion tank vent to shift the blockage in the line from the expansion tank. If that doesn't work he suggests we have no other course of action than to have the line from the expansion replaced section by section until the blocked area is removed.

Is there anything else that can be tried or is this really the only option open to us if the applying mains water at the vent does not work?

Any suggestions anyone has would be very appreciated.

 

[Softus]

Our plumber thought at the time that the line from the feed and expansion tank was blocked and that the system wasn't refilling (the ball cock valve works fine - you can push it down and get fresh water to enter the tank). Judging by the large amount of crud in the tank this seems a reasonable assumption.

Indeed it does.

A plumber is coming round tomorrow. He is suggesting connecting mains water to the expansion tank vent to shift the blockage in the line from the expansion tank. If that doesn't work he suggests we have no other course of action than to have the line from the expansion replaced section by section until the blocked area is removed.

He doesn't sound like a very experienced plumber.

You can usually go straight to the blockage if it's affecting the whole system (which yours is) - it's always at, or upstream of, the tee that joins the cold feed to the primary circuit. You can check with a magnet, which will be attracted to the ferrous 'putty' that forms the blockage.

Is there anything else that can be tried or is this really the only option open to us if the applying mains water at the vent does not work?

It's unlikely that mains pressure alone will shift it, but you don't need to dismantle the system systematically - just cut into the pipe above the tee and poke up and down with suitable poking-up-and-down implements.

 

[nickso]

he has to remove the blockage from the feed pipe by cutting it open. anything else is pure laziness IMO.

if its not accessible for some reason then the mains water trick can work but things can leak if he puts the pressure on an old system, sometimes causes more problems than it solves. its only really a temporary measure at any rate as its unlikely to completely remove the blockage.

if hes really struggling he could combine the cold feed and expansion pipework but thats a last resort.

 

[JohnD]

I'm thinking of using an Aquavac on the vent pipe, I've heard that can shift the blockage. Needs to be followed up with a chemical clean (and preferably a Magna thing) to shift and capture the debris.

IANAP

 

[Softus]

I'm thinking of using an Aquavac on the vent pipe, I've heard that can shift the blockage.

It can't clear a blockage in the cold feed, but you have a point because occasionally the blockage can be at the tee for the vent, which would also prevent the system from filling.

I once cleared a Gledhill vent with a wet vac, which was lucky because otherwise I'd have had to partially drain and dismantle a very hot appliance at the end of a very long day.

IANAP

R U sure the OP will get that?

 

[JohnD]

It can't clear a blockage in the cold feed

I was hoping it could (my old mum's house)

I know how to cut out and replace a Tee, but I'm a very slow and clumsy worker.

 

[nickso]

IANAP

R U sure the OP will get that?

never mind the OP....i didnt get it

 

[JohnD]

I am not a Potato

(Hint: For "potato" look at Forum Heading)

 

[Softus]

It can't clear a blockage in the cold feed

I was hoping it could (my old mum's house)

Don't let me put you off trying - you have nothing to lose except for a very few minutes of your time.

However, if/when it doesn't work, my advice would be to use the [magnetic] force, empty the F&E, and go for the throat of the problem.

I know how to cut out and replace a Tee, but I'm a very slow and clumsy worker.

Like all sparkies?

 

[JohnD]

Like all plumbers!

 

[Softus]

But I didn't.

 

[MOD 2]

topic is

 

[nickso]

topic is

at the top of the page

i think we are just killing time until the OP responds

 

[JandS]

Thanks for the advice. It sounds like we will end up cutting into the feed line to unblock it (if the mains pressure doesn't work) then following up with a chemical clean to clear the rest once we get some flow.

The pipe from the F&E tank looks like it is fairly convuluted so maybe the blockage won't be at the Tee but it sounds like a good place to start. Will remember the tip to check with a magnet.

 

[JohnD]

maybe the blockage won't be at the Tee .

It (almost) always is!