[bilproject]

Two things are necessary when treating surface water for drinking purposes. First is filtration to remove suspended solids. A cotton filter will remove solids from the water. Second you need to remove VOC or volitile organic chemicals such as oil and gasoline from boats. This is done with a carbon filter. Also, surface water tends to contain cysts which can be removed with a 5 micron carbon filter. Last we kill the bacteria by bathing the water in UV light.
So a good system needs to incorporate all 3 of these parts. How often you have to change the filter will depend on your intake. The deeper the better as there are less suspended solids and alge gowth is less the deeper you go. If your intake is close to shore wave action really stirs up and suspends solids. The UV will not change the taste of water and there is no residual effect. The carbon filter will make your water taste as it should, like nothing.
Google UV water treatment and many manufactures will come up. You will need to decide if you are treating all your water or just water say at the kitchen and bathroom sink.
Filter changes will depend on the clarity of the incoming water. On the northwest side of Bear I change my filters every 30 days as flow drops off. My intake is 200 ft from shore in 35 ft of water. Be sure to keep the foot valve off the bottom.
Since your application is seasonal and the system is shut down and somewhat open over the winter you need to disinfect your piping by adding a cup of bleach to a filter canister and flushing it into the piping when you turn the water on to kill any bacteria in the pipes. Remember the UV light has no residual effect so your clean water will be contaminated by bacteria in your pipes after the UV unit. Wait 2 hours before fushing out the clorinated water and remember if you have a septic to flush it into buckets not down the drain. Do not want to kill the good bacteria in the septic. Clorine will gas off in 2-3 days