I had trouble with air getting in the pre filter in exactly the same was as described earlier in this thread and was absolutely sure the o-rings were fine. I came up with the same idea- buy a little plastic strainer and ditch the one in the filter housing.

That said, does anyone know where I can buy a viton o ring kit in the UK, or where there is a list of the sizes I need?

Also, does anyone know whether I need to switch the o rings in the IP to viton to run SVO (as well as all the other kit)?

Thanks

Jon