Mitch brought next idea :
Is there a bath sealant system that exists that actually lasts more than
about a year? I have tried stick on strips (very poor), corner tile type
strips with sealant (better) and good old thick branded sanitary sealant
(from tubes) to seal the small (c. 2mm) gap between my plastic bath and the
wall tiles. But inevitably after about a year a small leak will develop. Has
anyone a recommendation of something that lasts a lot longer?

The stick on strips do work very well. Its a matter of making sure the
area is scrupulously clean and apply pressure all the way along them to
get them to stick firmly - a roller does this best. The only problem I
have had is with slight shrinkage back away from a cut corner.

With a plastic bath, I would suggest filling it up with water before
starting, so as to make it deform to its maximum.

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Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk