Kent Maxima RO Filter Question

[grumpygils]

I have a Kent Marine 4 stage RO/DI unit. It has seemed to be working fine but it was time to change the filters. Few Questions. The first chambers is the standard white prefilter. I inserted it in and have run for about 25-35 gallons and it has not turned brown at all. It looks brand new. Shouldn't it be turning brown a little? This lead me to think it was not seated properly, so I re-did it and ran. When the system recharges with water on the initial fill after new filters, shouldn't the water come from the bottom of the filter? It should go through the center, down and out through the length of the filter? When I refill the system, the water appears to be going down the center and the sides (alot). This makes me think that the filter is not seated right? The other two chambers have rubber gromet fittings. As I write this I am thinking that the first filter also has a rubber gromet fitting and they were stuck to the old filter and I pitched them? Does any one have this unit and know?
Thxs,
Mike

 

[scsinet]

If the filters weren't seated right, you'd know. Either you wouldn't be able to close the canisters or the cartridges would get crushed and you'd have noticed it when you tried to re-seat.
It sounds like everything is working fine.
The sediment filter does not have gaskets.
The sediment prefilter will turn brown eventually, but not after 25 gallons or probably even 250. When I change my sediment filter, it takes months for it to turn brown. I might notice a tinge after a few weeks, but that's about it. I use an average of 5 gallons per day of RODI, more on water change days.