shiner, mines a 300 roman the instructions that come with it
say replace after 6 mths its a 10in
very little is said about membrains
is your view an educated guess or what?
maybe you tried my trick.....or similar, and got membrane
damage as a result
ichecked my inbuilt meter and handheld.....exactly the same
I used to have a 300 gdp like the ro-man one. I wasn't aware about changing the pre filters and my membranes were wrecked after about 9 months. The pre filters were 20".
I know now that the 20" ones are meant to be changed 6 monthly. The info about changing 10" filters quarterly, I read on here some time back (it must be true as I read it on here

). The 10" info was not queried by anyone so I took it as true.
If you have product instructions to change them 6 monthly then it appears that what I read may have been incorrect. Either way, 8 months is too long.