I own a Sears UltraFilter 350 water filtration system. There are 3
filters - pre-filter, reverse-osmosis filter, and a post filter. I was
told I had to replace the pre & post filter every 3 months and the RO
every 2-3 years or so. I just replaced the pre and post filters. The
pre-filter looked quite dirty, but the post filter looked perfect. Can
I get away with changing the post filter much less frequently, waiting
until it looks dirty, or is this a bad idea?

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Clarification of Question by costaricaraftguide-ga on 30 Oct 2005 21:40 PST

What if I re-use the post-filter, using it as a pre-filter (they are
the same) since the post filter is in such good condition?

hello,

normally the first filter will do a 'rough filtering' and the third
filter a 'fine filtering'. because of this, you will not necessarly
see the third filter getting dirty.

if the second and the first filter are really the same, you could use
the third filter as first filter too.

in normal conditions you could also change the third filter less
frequently, since it shouldnt be as fast 'dirty' as the first filter.

keep in mind, that you should normally notice if the watter is really
getting worse.

regards bd