Cutting a hole in a flue pipe

[Minkeycat]

Our boiler vents steam up a 1m length of 4 inch vitreous enamel flue pipe that goes through a sealed registry plate with no access through it and is connected to a flexible, stainless liner that then goes straight up the chimney and out of the top. It's been like this for years but we've just changed insurers and the new ones have said we must now have this flue cleaned twice a year. This means that I must cut an access hole for the sweep to be able to get his brushes into the flue. The hole will be covered by a stainless steel, oval plate that I ordered today. This is an "eye patch" type of plate that attaches by a screw on either end.
My questions are;
1. Will a round hole be OK? (I'm assuming I can buy a holesaw for a drill that goes through metal)
2. What size hole would be needed to access a 4 inch pipe?
3. If I can't use a drill, how best to do the job? The flue cannot be moved as it's fixed at both ends and snugly goes through the fixed registry plate?
Many thanks in advance for suggestions.

 

[CliffordPope]

Why does a steam vent need sweeping - it's not a flue with smoky combustion products?

 

[Craig89]

Agreed, surely this is a missunderstanding on the insurers part

 

[88v8]

A steam vent? Errrm, wossat?
What is this boiler and what fuel and where do the combustion products go?

I'm not sure a standard hole saw will cut into a pipe that size. First, the vitreous enamel will blunt the saw, but leaving that aside, two edges of the hole will cut through completely with the other two edges not even started, so it may jam up, and the saw will need to be jolly deep or it will bottom out before the hole is fully cut.
I'd practice on a piece of plastic (drain) pipe first.
There's also the question of maintaining enough pressure on the saw to make it cut, as opposed to rubbing over the surface which will blunt it.
See here
https://weldingweb.com/showthread.php?217511-Cutting-holes-in-steel-with-hole-saws

You'd need to make a gasket to go between the cover and the pipe, if you do manage it.

We don't even sweep our woodburner twice a year - yes we are supposed to, but with the dryn4ess of the wood we burn, I don't.

Ivor

 

[Minkeycat]

I totally agree with the "Why does that need sweeping?" question. It seems to be because we have a thatch. We changed insurers who are stating that "all chimneys and flues in use" must be swept twice a year. This flue is in use so must be swept. Initially the heating engineer who services the boiler AND the sweep said it was ridiculous so I told the insurance brokers and they said to get it in writing from either of the trades and they'll tell the insurers but they then changed their tune when I asked for written evidence of their claims. It's an oil boiler. It just vents up the chimney and steam of some description comes out the top as it has done, via a stainless steel liner, for over 10 years. This particular saga has been going on since Christmas because the sweep hasn't been able to get hold of an access hole cover because he was told they simply don't exist. I got fed up with the situation and being told we won't be insured if we don't get it done and they won't cough up for *any* claim if we make one. (Presumably a sealed flue not being swept can make a burglary more likely?!) Anyway, the first person I rang yesterday had a cover and I thought I'd take it from there.

I wish we hadn't changed insurers. This flue hasn't been swept since installation. I'm not a heating expert of any description but I'm expected to be one. This whole thing has made me want to move house to somewhere with a proper roof! So far, saving £200 by changing insurers will have cost much more than that by the time this is sorted. Lesson learned I suppose.

But I appreciate the information about cutting into the pipe. I might look into other tools.

 

[CliffordPope]

"all chimneys and flues in use" must be swept twice a year. This flue is in use so must be swept.

It isn't a flue - it's a steam vent pipe. How did the insurance company ever know to raise the matter?

 

[88v8]

So this is a condensing boiler? Doers it have to vent into the chimney, could it just vent through the wall? Dunno, I'm no expert on oil boilers.

Ask the manufacturers whether it needs sweeping, if they say not then get it in writing.

As to cutting a hole, just found this, the first section may be some help
https://www.youtube.com/watch?v=7tCuu2pO0fI
I guess he just used a jigsaw.

Thatch is lovely to look at but a pita and a moneypit to live under.

Ivor

 

[Flyfisher]

How about contacting the boiler manufacturer for their recommended maintenance procedures? Presumably they should be able to give a suitably ‘expert opinion’ that would satisfy the insurance company.

My non-expert view is that if the flue required such regular access then the manufacturer would have provided an access point, but I appreciate that such logic is unlikely to satisfy an uninformed insurance company. Also, if the boiler was gas-fired I’m pretty sure it would be illegal for anyone other than a ‘gas safe’ qualified person to make any such changes, but I’m less sure about oil-fired ones.

How about asking the insurance company to provide you with written confirmation that they will underwrite the required changes to this flue so that it can be maintained in the way they seem to require? Of course they won’t, but perhaps it might make them think about what they are asking.