The simplicity of an effective on board water system is: CLEAN
Seasonally, you really should inspect for the growth of bacterial slimes, etc. growing on tank walls, etc. and if present you really should/have to mechanically scrub them away, followed by shock sanitization with simple Clorox (@ 40 oz per 100 gallons at 1-2 hour 'soak time') then thorough rinse. When you reach inside the tank on your yearly inspection and your finger finds 'slimey' when touching the tank walls .... thats a bacterial slime and should be scrubbed away. If you have insufficient access to the tank internal for cleaning/scrubbing, then I recommend SEVERAL and repeated 'shock sanitizations' with 'clorox, etc'.
If the tank is aluminum (aluminum reacts with chlorine to form aluminum chloride) then very diluted clorox FAST rinses ... and hope for the best.
Simple hygienic 'cleanliness', same as you would apply to that jug of water you haul around, it the simplest approach. Think 'kosher' or more correctly 'parve' which translates to 'clean'.
Filters - do the bulk of filtering BEFORE the water is in the tank.
Dockside hose - apply screw-on filter of at least (in the USA) that is 'certified for the removal of oocysts'; or, at least 1.2΅M at 99.9% removal efficiency ... or 'something similar' on the filter packaging. This will remove most all the harmful protozoa, etc. that 'can be' present in municipal water systems and that are immune to chlorine sanitization. Obviously this level of filtration will remove most 'visible particulate'.
Carbon packed 'filter' (add downstream of the dockside filter). Its job is to remove dissolved organics and inorganics ('taste', etc.). Run this filter as SLOW AS POSSIBLE as this is an adsorption process and 'contact time' of the water,etc. TO the carbon is important in the efficacy of removal. DRAIN and shake out all the water when finished 'filtering', store this filter 'dry'.
Dockside Hose - 'certified for use with POTABLE water' - ONLY. Less PVC fragments and leachables (taste and nervous system 'destroyers') that way.
System inspection and maintenance.
Yearly clean out and shock sanitize, mechanical scrubbing if needed to remove 'slimes'.
Shock Sanitization dosage: 40 oz. of grocery store Clorox per 100 gallons of water - let soak 1-2 hours then dump, then rinse and dump again.
Change out / replace ANY (clear) hose, etc. component that has become 'dirty looking' ... clear plastic hose when 'penetrated by fungals, etc.' will look 'grimey'. Look for hose that is "certified compatible for POTABLE water" - your brain and neuro-tissue will thank you.
Start out with a total replacement of the entire VENT line .... replace with reinforced clear water hose, etc. .... and then put a FILTER on or near the end closest to 'outside', etc. to prevent the aspiration of molds, mildews and airborne bacteria. Can be as simple as taking a fist size 'wad' of absorbent 'first aid cotton', taping to the 'end' and then covering with 'bandage gauze'. Keep dry and replace yearly.
Maintenance dose of 'clorox' to attenuate 'biological growth':
Standard dosage: 4oz. of grocery store clorox per 100 gallons of water
Best dosage: Have your WIFE smell the water as it comes out a spigot, you want her to discern the 'barest possible hint' of chlorine in the effluent water. If no 'hint', then add clorox until she can discern the 'hint'. If more than a 'barest hint', dilute the tank with MORE water.
NO chlorine added to aluminum tanks .... youll eventually 'burn a hole' in
Fiberglass water tanks ... remove/replace, certainly dont DRINK the stuff - PERIOD.
On board filters. Not really necessary if you did all the preliminary filtering and cleaning and 'dosing'. If the tank water then develops a 'taste' then you have some component that is leaching chemicals ... find it and get rid of/replace it.
On board filters -
I'd avoid 'carbon filters' under the sink for several reasons:
a. will remove and adsorb any 'chlorine' that is used to 'maintenance dose sanitize' the tank water .... even if the water is NOT flowing through the filter.
b. will 'concentrate' any bacteria, etc. that it 'captures'
c. the carbon can become a potent nutrient source for bacteria and other microorganisms
Take on board only the amount of water that you're going to use within a reasonable time. The less amount of stagnant water left in a tank, the less 'biological growth'.
hope this helps.
I would add too that you should use Clorox and not generic/store brand/dollar store bleach, as the cheaper stuff is often of unknown strength. One of the ways they make it cheaper often is to just dilute it.