13-12-2019, 08:07 PM
Back in March 2016 I started this thread about failure of the flow hose in my Viessmann boiler. I decided to change it again as a precaution, now that the replacement hose is almost 4 years old. My local plumber's merchant (where I bought the boiler) ordered the hose for me and I decided to fit it this afternoon. I was anticipating a fairly quick and easy job. I was mistaken
Turn off boiler isolator valves, gas and electricity. Depressurise boiler. Disconnect top of hose which is easy. Oh dear, it's absolutedly full of black sludge! Bottom conenction is harder to reach but I worked out how to do it. Hose really is full of sludge. As is the pipework in the valve/pump assembly.
Not surprising that the system hasn't been heating up very fast. It gets there but takes a lot longer than I remember and I was planning to investigate. There's precious little space for water to flow at all, I reckon it would have failed completely soone enough. The hose is in pretty good condition despite al this. Where did all the muck come from? I acid cleaned the system a couple of years ago and used plenty of inhibitor. But I don't think I flushed the boiler itself just the rads and pipework. There may also have been residues of solid sludge at the bottoms of rads where the acid didn't get all of it. The Magnaclean should have picked it up on the way past but who knows.
Anyway, I've got to take the whole pump/valve etc assembly out of the boiler which is a fair bit of dismantling. Plumbing and electrics. Found that the flow side was very mucky but easily flushed. The return side (including the pump) was pretty clean. So got all that done. I also though it would be a good idea to flush the heat exchanger and return hose. I could feel the crunch of sludge as I squeezed the return hose. I rigged up hoses to reverse flush the heat exchanger and return hose with mains poressure. Got a lot of muck in the bucket. I ought to replace the return hose but that means taking out the entire burner assembly. And getting a hose, which isn't off the shelf.
After a fair bit of cursing I got the whole thing back together and it seems to be heating the rads faster.
I'm left with a couple of problems. One is a tiny bit of water that got to the ceiling below. Easily fixed. The other is a nuisance. The isolator valve on the flow side is now dripping from the gland. It's a common problem with quarter turn valves and AFAIK there isn't a cure. So it's a new valve plus depressurise whole system etc etc. For now there's a bucket under it and the rate of loss is low enogh that I don't have to take immeediate action.
The valves are shown here. The flow vlave is the lower, simpler one: https://www.viessmannspares.co/Flow_Retu...71857.aspx
£78 is a fair bit of money, haven't yet found it available separately from the return valve. I'm thinking of using a 22mm to 3/4" tap connector and a decent quality seperate quarter turn valve. It i will need some minor plumbing changes but nothing complicated. Not 100% sure about how a tap connector will fit. The boiler has a male 3/4" thread, much like a tap. The fitting on the valve looks like a tap connector but has a flat mating surface with no flange. It takes a standard 3/4" tap connector washer.
Turn off boiler isolator valves, gas and electricity. Depressurise boiler. Disconnect top of hose which is easy. Oh dear, it's absolutedly full of black sludge! Bottom conenction is harder to reach but I worked out how to do it. Hose really is full of sludge. As is the pipework in the valve/pump assembly.
Not surprising that the system hasn't been heating up very fast. It gets there but takes a lot longer than I remember and I was planning to investigate. There's precious little space for water to flow at all, I reckon it would have failed completely soone enough. The hose is in pretty good condition despite al this. Where did all the muck come from? I acid cleaned the system a couple of years ago and used plenty of inhibitor. But I don't think I flushed the boiler itself just the rads and pipework. There may also have been residues of solid sludge at the bottoms of rads where the acid didn't get all of it. The Magnaclean should have picked it up on the way past but who knows.
Anyway, I've got to take the whole pump/valve etc assembly out of the boiler which is a fair bit of dismantling. Plumbing and electrics. Found that the flow side was very mucky but easily flushed. The return side (including the pump) was pretty clean. So got all that done. I also though it would be a good idea to flush the heat exchanger and return hose. I could feel the crunch of sludge as I squeezed the return hose. I rigged up hoses to reverse flush the heat exchanger and return hose with mains poressure. Got a lot of muck in the bucket. I ought to replace the return hose but that means taking out the entire burner assembly. And getting a hose, which isn't off the shelf.
After a fair bit of cursing I got the whole thing back together and it seems to be heating the rads faster.
I'm left with a couple of problems. One is a tiny bit of water that got to the ceiling below. Easily fixed. The other is a nuisance. The isolator valve on the flow side is now dripping from the gland. It's a common problem with quarter turn valves and AFAIK there isn't a cure. So it's a new valve plus depressurise whole system etc etc. For now there's a bucket under it and the rate of loss is low enogh that I don't have to take immeediate action.
The valves are shown here. The flow vlave is the lower, simpler one: https://www.viessmannspares.co/Flow_Retu...71857.aspx
£78 is a fair bit of money, haven't yet found it available separately from the return valve. I'm thinking of using a 22mm to 3/4" tap connector and a decent quality seperate quarter turn valve. It i will need some minor plumbing changes but nothing complicated. Not 100% sure about how a tap connector will fit. The boiler has a male 3/4" thread, much like a tap. The fitting on the valve looks like a tap connector but has a flat mating surface with no flange. It takes a standard 3/4" tap connector washer.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
