I have inherited a pond - or rather series of 3 ponds connected with water
falls that were made using one single sheet of butyl rubber.

I have begun losing significant amounts of water and have tracked it down to
a hidden section of liner dipping just below water level when the waterfalls
are going. I have exposed the faulty section that was hidden by morter.
Originally the morter nearly sealed the area but appears to have been worn
away by the slow passage of water.

I would like to attach a strip of rubber liner to the existing edge to
effectively raise the edge by an inch or so. I have initially tried using a
strip adhesive on a roll that is carried by a white backing paper - not sure
of the name but intended for sticking patches to the liner.

Due to (possibly) insufficient cleaning of the existing liner and/or the
very creased undulating existing edge it does not appear to stick as well as
I would like.

Anyone any other solutions? Any mastic like substances that will stick to
the butyl and give additional help? When completed it will be covered again
and not subject to significant movement.

It is not really practical to lower the waterfall to lower the water surface
below the edge.

JohnB