Can someone explain this to me?
 

Five years ago I installed a Pura UV20-3 whole house water filtration system for our lake water feed. The system is comprised of three components in series: first there is a 5 micron wound sediment filter, second is a 10 micron carbon filter and third is a UV light. Currently my lake pipe is installed in shallow water (< 4') so wave action caused quite a bit of "stuff" to get sucked into the system which causes me to have to replace filters at least monthly because water pressure at the faucet becomes significantly diminished. Comparatively speaking the sediment filters are approximately a third the cost of the carbon filter which I thought would be a good thing because the sediment filter would stop everything 5 microns or larger in size and the carbon filter would let anything smaller than 10 microns through ....... So (in my mind) the carbon filter should never get clogged up. In reality how ever it is the carbon filter that is the bottleneck and needs to be replaced first (or at the same time as the sediment filter). How can this be, it just doesn't make sense to me!!! How is it possible for a 10 micron filter to get clogged when only particles smaller than 5 microns are getting passed to it? What is it that I'm not understanding?

I think you should try a 5 micron sediment then a 50 micron sediment. There is no sense sending all your house water through a carbon filter. If you want a carbon filter, put a small one under the sink where you draw your drinking tap water from. This is exactly what I do and I only change my filters once during the summer and I live at my camp daily not just weekends so we use a lot of water.

Also if it's possible to get your water line out in deeper water that would make a big difference.

Dan

http://www.baldwinfilter.com/literat...9;s/89-5R3.pdf

The gist of it is that there are different test methods used to rate the filter media and clearly your two filters did not use the same method. Look for a different sediment filter cartridge.

Since you are pulling water from the lake, rig up a back flush to occasionally blow the crud back out into the lake and prolong the life of the cartridges. With a backflush setup, you can only use one filter though, not two in series. You could also rig up a second filter in parallel with valves that let you switch from one filter to the other instantly that you always have one clean filter ready to go and have no urgency swapping the element in the clogged filter.

Filter Tank with Garnet
 

We also draw water from the lake, but instead of a cartridge filter we have a resin tank filled with garnet. It automatically backwashes once a week to the outside. We don't do much to maintain the resin tank. I guess you could replace the garnet periodically, but we never have (10+ years).

The backwash controller can measure gallons of use or time (days between backwashes). The gallon meter broke a few years ago so we just do time.

During the backwash, a small secondary tank filled with bleach and water supplies a solution to sanitize the resin tank. I suspect that reduces odor.

The resin tank is about 4' tall and 8" in diameter, filled about 3/4 full with garnet.

After the resin filter tank, we have a UV sterilizer, then a point-of-use carbon filter at the kitchen sink.

We did a water test a couple of years ago, and the results were fine.

It's conceivable that the garnet filter isn't doing 5- or 10-microns (whatever the UV sterilizer is rated for) but it all seems to work well.

So, you might check into the addition of a resin filter tank upstream of your cartridge filter. You'd have to get a plumber to install it.

Each filter is removing different things from the water. If your carbon filter is blocking up I definitely would not recommend removing it for another sediment as voc's or something organic is being filtered out. The carbon filter removes things like dead algae, gasoline, etc.
Your best solution is to first get that intake in at least 9 feet if water supported off the bottom. Second you could go to a coconut carbon filter of the same rating as they seem to have a little more capacity or longevity. I have been using the same system for 10 years. We are here from mid may to mid October. My home has 2 full baths and I filter the whole house. I change filters about every 6 weeks.

location, location, location
 

I strongly agree with those who suggest, FIRST, move the intake into deep water. While water quality varies from place to place, that's a universal fix. Then send a sample to a lab and see what you really need to filter. Our lab results came back OK with just a little bit of bacteria. NO FILTER in the system, except the aerator on the tap, which never clogs. The ice maker never clogs, either. We used to have a filter that kept clogging with iron. When we switched from galvanized pipe to a PVC intake pipe, 35 years ago, we stopped using that filter. Our pump is a well type that is at the intake, 10' deep. Never had a problem, and we never hear it run, unlike the old jet pump under the building.