We do manufacture a 90mm valve.
The 80mm is practically the same OD as the 90mm stormwater pipe.
The socket ends are simply trimmed to fit.
Aussie Koi WA, designs and builds high quality fish ponds. We have been using OzValves for over 10 years and they have proven both cost effective and superior to other similar valves on the market. We have not had one complain and never changed a set of seals in this time. We also like the fact that it is possible to change the internals without cutting out the valve from the line, not that we have ever had to do this but this was the original attraction to the valve. Add to this good friendly reliable service; we have no hesitation in highly recommended them to others.