"Jenny" wrote in message
...
Hi what would be the best glue to use to glue plastic tubing to small
plastic pots that would be full of water. I was going to use silicone
sealant but it says not to use in permanently damp conditions. The joint
would in water all the time. This is to make a watering system for a
greenhouse.


Thanks, Jenny

Do you know what type of plastic you are trying to glue?
Are the tubing and pot made of the same material?
Do you really need to glue at all?
PVC, ABS, Nylon - in its many forms -, Polycarbonate; Polythene;
Polystyrene; Silicone rubber; PET... the list goes on and on.

Some, like PVC, have oily plasticizer chemicals in, and are a nightmare to
stick, without purpose made adhesives. In most cases you need to be
sticking like to like, with like. Plastic plumbing kit would have all of
these things matched of course...

[One basic way we used to test plastic, was the 'burn and sniff'. This
won't be able to help with detailed analysis, but, if two pieces of plastic
are similar, they will behave the same and smell the same when you try to
light them. Cut a small piece and hold it briefly in a flame; waft
cautiously, a little of the fumes towards you and note the smell - don't go
inhaling! Some will light and burn with a black smoky flame; some will burn
with a clear blue flame and drip; some will not burn; some will only burn
while in the flame, and go out as soon as you pull out; some will burn with
melting; some (nitrocellulose!) may go up like a rocket; so the emphasis is
on the SMALL test piece: a millimetre cube is usually quite enough. If your
two items to be stuck are of plastic that behaves in similar ways, the
chances of you successfully sticking them together will be greatly
increased.]


Easiest way to make sure you have a watertight system would be to use
standard plastic plumbing pipe, glue (or better still 'speedifit') fittings,
that are really quite cheap online from eg Screwfix.

Another way would be to use bungs/corks, and 'home brew' kit type plastic
tube, and no glue at all.
Easiest way to make neat holes in plastic of numerous kinds (I do a lot with
plastic bottles), is to use various nails, bits of different sized metal
tube, etc, heated up on the gas ring, and just push through - gives a clean
hole that is less likely to split than if you try to cut or drill.

In fact, thinking on this: why not use whole plastic bottles, upside down,
with a hole through the cap for your tube - make a hole in the bottom for
filling.

(Incidentally, another handy use for old plastic bottles I've recently hit
upon, is to tidy away my ethernet cables - I have some 20metre ones - in a
way that minimises tangling: Get a 2 or 3 litre 'coke' bottle; melt a hole
in the bottom with a piece of copper plumbing pipe - or you can use a hot
nail and wiggle it around till the hole is big enough - just big enough to
thread your ethernet plug through; feed cable right through the bottle, and
slide it down nearly to the router or whatever; when not using the cable,
you can then feed it all into the bottle from the cap end and it usually
spirals in fairly neatly, with a shake or two, ready to be quickly pulled
out when next needed.)

You might also, not bother to make any holes at all and simply put home brew
taps in your flexible tube so that you can fill it with water and simply peg
the top end under water in your pots so that it just siphons out at whatever
rate you let it via the tap.

On the other hand, the real lazy way, would be just to get big plastic
bottles and make pin holes in the bottom: then you can just stand them among
your plants and regulate how fast they empty by tightening or loosening the
top.

Lots of ways to do this one!

Have fun and save us some tomatoes.

S