On 08/05/2021 13:03, David wrote:
On Fri, 07 May 2021 16:34:52 +0100, Chris Hogg wrote:

On 7 May 2021 14:31:38 GMT, David wrote:

Wearing my "long time since I did this" hat.

I have a connector kit to join two water butts.

The diameter of the non-threaded bit is 24mm.
Outer diameter of the thread is 25.64 mm.

So do you cut the hole to be a tight fit (24 mm) and expect the
connector to cut a thread which seals, or do you cut for a loose fit (25
mm or even 26 mm)so the connector just slides in and the seal is on the
mating faces with the water butt plastic?

I'm about to go shed diving again, but the cutters at Screwfix are 25mm
which might be a hint.

Cheers



Dave R


On my water butt connectors, which are like this,
https://tinyurl.com/yjqlwtnmthe the threaded portion is a loose fit
through the hole in the butt. There is a plastic nut and a rubber
washer, and the plastic nut is tightened up to compress the rubber
washer against the wall of the butt and achieve a seal. The corrugated
hose between the two barbed connectors is a fairly tight push-fit onto
the connectors. Softening the hose slightly in hot water before
applying, helps. I applied some gutter sealant liberally over the
washer, the nut and the barbed connector to ensure a good seal. Didn't
bother with hose clips - didn't need them.

Thanks.

A vote for a loose fit and use the washers to make the seal.

That would be the normal approach using a plastic "tank connector". But,
with a metal plumbing fitting in a thick enough thermoplastic tank you
can get away with using the fitting as a "tap" in an undersized hole,
especially if you have a back-nut for extra security. A sealing washer
may not actually be necessary, especially if you put a smear of sealing
compound on the threads and the internal and external faces.


All the cutters I can find seem to be 25 mm which may be a tight fit but
will check what the next size up is.

Don't think I can go above 26 mm for the hole and still have enough
surface for the washers to seal onto.

The main upside is that the connectors will be right at the top of the
water butts so a little leakage will not be a major problem, unlike the
taps at the bottom.

You can use the same approach for taps, especially if they have a decent
length of thread so that there is plenty of room for a back nut.


Cheers



Dave R