What would you recommend? I assume a pre filter and then a fine filter.
In your earlier post you gave the figures as "2-3 micrometers
absalute".When I see filters in our local hardware store they say what
they will do,i.e, protect from cysts, but not the actual size. Are
filter elements standard sizes?
Tony


The hardware store filters are not accurate in their retention size. In
fact what they represent is "nominal" rating, which in filter-speak
jargon can mean anything from 50% to approx. 98% removal efficiency (by
weight) at the 'rated' retention size. The rating can be ANYTHING the
manufacurer wants it to be! .... and doesnt (usually) mean that such and
such 'micron rated' filter will retain all such and such particles!!!!
Hardware store type filters are not meant to be used as a 'single pass
filter'; but, are meant to be used wherin the fluid is re-circulated
several times throgh the filter to attain an 'approximation' of the
rating - such as in a (recirculation) swimming pool filtration set.

With cysts, etc. the (very loose) NSF regulations require approx. 98%
removal (by weight) at 1,0 micrometers per single pass of the fluid.
Without an accompanying validation statement on the filter package I'd
be quite dubious of its *true* retention rating ... yes, they will
remove cycts, but probably not to the level required by the NSF regs.
Sadly, most of the 'hardware store' types of filters are rated in the
same manner that manufacturers promote snake-oil. You usually get what
you pay for... a hardware store filter typically in the $2-$6 range, the
same (but precise and compliant) filter from a technical manufacturer
will be in the range of $15-25.