On Sun, 6 Jun 2021 23:32:19 +0100, newshound
wrote:

snip

Or, for less effort, you could use a 3 inch bulkhead fitting or tank
connector (same thing, two different names) connected with flexible
hose. You might get away with a 2 inch.

I think Tim was quite specific in his requirements (if not directly
mateable to 68mm stuff). ;-)

Well the short answer to that, AFAIK, is that the only official fittings
you will get for drain pipe are for gutters, spouts, and tees. And I
agree that the petal approach should work if the penetration has to be
67mm pipe.

And he's in there fibreglassing 'anyway' etc. ;-)


Also, if he does line this tank with fibreglass he might need to glass
in a smooth collar of some sort if using a bulkhead / flanged fitting,
or use some additional sealant to ensure it seals against the back of
fibreglass?

There's a choice there, if the tank is good he can seal against the
tank, and then fibreglass over it.

I'm not sure I'd like that as you are sorta then relying on getting a
good seal 'outside' the actual water container (now a fibreglass box
inside a galv tank). ;-)

Alternatively try to get a smooth
layer of fibreglass that the standard washer will seal against,

I would finish the glassing with a couple of layers of fibreglass
tissue and then lightly clamp a flat object on top with a layer of
something non-stick in between.

or
perhaps use a thick washer made from closed cell foam.

Yes, or a thicker / softer rubber etc.


I made an interesting discover the other day. I needed to fit some of
this stuff (two inch, actually) over the threads of another fitting that
was just too big. I popped the end of the hose in boiling water for a
minute or two and it became soft enough to push straight on.

Was the 'discover' doing that on that large a profile or in general?

Well, it was on two inch MM pipe that was definitely not going on to the
threaded boss "cold". I've often used the hot water trick on garden
hoses, and on various nylon or PVC "fuel pipe".

Ok.

But I was interested to
find that the reinforcing "spring" in the Machine Mart hose, which is a
very tough thermoplastic, does in fact soften very satisfactorily in
boiling water while still retaining enough strength to grip when pushed
on to the threads. I just thought others might find that information
useful. The pipe looks and feels superficially as though the "spring"
could be metal, in which case of course the approach would not work.

Agreed. It look far less likely that it might all (as you say, inc the
anti-crush reinforcement) respond to heat but seems to.

I've done various other sorts of bodge on that type of hose before, on
the previous connection I needed to attach it to something like domestic
sink waste pipe, and I did that by wrapping the pipe with Sylglas/Denso
Tape and twisting that inside the MM hose. Followed up with my favourite
wrapping with PVC electrical tape under tension.

The trick with all that sort of thing is understanding the mechanics
of what is going on. I've seen people try to join / fix fuel hose with
insulation tape and seem surprised when it more or less melts or
un-glues in front of them or things that instantly burst off out
though because of pressure.

snip

Cheers, T i m