Any RV water system is only as good as the care and maintenance that goes into it. All systems should be decontaminated at least once a year. Depending where I've been, I may decontaminate mine 3 times a season. Once purified water goes into a storage system care must be taken to prevent cross contamination. In other words don't let your shower head lay on the ground or let your pets lick your sink faucet. Take a look at the source of the water, use common sense.
The first filter on this system is 1 micron. It costs $7. The second is .1, .4 nominal. It's replacement cost is $65. It makes much more economical sense to sacrifice the $7 one than the $65 one.
The UV purifier must have a turbidity of 1 micron or less otherwise shadows will be created and not allow full disinfection.
Below is a link that shows the lab results of the Seagull filter.
http://www.seagullwaterpurification.com ... alysis.php