Truma Ultraflo?

Lunar Solar Lx2000. No filter kits available for the existing system.
Changing the Carver Crystal 3 water housing to a Truma Ultraflo pistol type pump connection.

The existing pump housing has a push fit joint on the back of the housing (feed in after leaving the filter) Can't get hold of Truma but wonder if anyone fitted one and used push fit. All other internal joints are releasable push fit. I just don't want to put the push fit on the new housing only for it to blow off with pump pressure.
thought I'd add the pump is submersible type dropped in barrel.
I won't be using the winter or external shower connection.

Ok not a repair but need advice can't find any elsewhere.
Many thanks