Help! Local charity had one of these installed by well meaning cowboys.

Just been to take a look. It has plastic screw threaded fittings on the
top in blue and red for water in and out. The guy who put it in must
have got both on cross threaded first time around and then over
tightened to try and stop it leaking. Several people have tried to sort
it out since with no success. They have already had two biggish floods!

Someone else has put them on properly threaded and then over tightened
them even more. It still leaks at a level where after an hour about 0.1L
escapes. Both hot and cold sides are compromised but hot is worse. There
are rust marks running down the side from the connectors.

This might be irrelevant but it is rated 2.2bar maximum pressure but I
am told as originally installed it was set on 3bar (despite what the
rating plate said). Will this have done any permanent damage?

I was thinking of taking it apart and putting Viton O rings around the
pipes and then tightening the compression fittings again. I also have
PTFE tape and circular section but I am undecided which would stand the
best chance of working. Any other suggestions for how to make the thing
leak proof - any magic gunks that would be worth a try. Bearing in mind
that it will get hot and cold cycled so anything too rigid will fail.

I hate plumbing but I am the best chance they have of getting a repair
for free - otherwise they will be buying an entire new unit (again).

Thanks for any tips or suggestions on a better way to proceed.

--
Regards,
Martin Brown