There are many ways to stay safe with water. We used to do what Steve does - filtering on the way in & out when we had our bus. Less room in the patrol called for a different method. Now we just filter on the way out. We use 1 micron solid block carbon filter impregnated with silver. The silver bit helps prevent any build up of nasties during periods on non use. Lots of filters out there to prevent bad tastes etc, but only those that specifically state that they are good for blocking the nasties like E.Coli, Giardia & Cryptospiridium (Sp?) will do so. Essentially you need an 'absolute' rating of 1 micron or less to do this I think. Many filters look good in the advertising, but when you look more closely they wont protect you against those 'bugs' which are what are the biggest risk from unknown water sources.
The B.E.S.T filters are certainly well thought of, but are quite expensive compared to others. I think (but could be wrong) that they contain granulated carbon. With granulated carbon the lower micron figures cannot be guaranteed because of the air gaps between the granules. This is where a solid carbon block is better. I used to use the standard 10" filter housings with appropriate filters. The advantage of these is that you can get replacement filters at just about any hardware store. The more expensive filters require you to use there replacements which generally cost more & are not easily obtained in out of the way places.
In the interests of saving space I changed to inline filters designed for chilled water outlets in the Patrol. They are a 'disposable' filter, but have been lasting us well. I change them if the water tastes bad (not yet happened) or after 12 months depending upon use. Last time I changed one was because it had sat unused for 7 months in a hot tropical climate. I had a couple of spares & thought it best to change even though the water was tasting ok. Having suffered the effects of 'bad water' in the past, it's not something I want to repeat. These are the filters I use. (Suitable micron size with silver in this size filter are not easy to find).
https://www.ebay.com.au/itm/12-x2-5-...F/121121928734 A cheaper similar filter , same size but no silver, is one that we've used when knowing we will be using our water daily for a while (& therefore don't need the 'storage capability' of the silver.
https://www.ebay.com.au/itm/Inline-F...e/263274679052 this is 0.5 micron. Generally they come with click on hose fittings, so easy to change. I have found the plastic fittings have a limited life on corrugations, but have had no breakages since I switched to brass fittings. Plastic are OK, but ask for a few spares to carry.
Pumps. Shurflo are good. We had a 10lpm 'Whisper King' in our bus. I made a few mistakes with the Patrol. Started off with a 17Lpm pump. Ridiculous & used far too much battery power. Then bought another Shurflo like we had in the bus - now carry it as a spare. At the time we were using garden hose trigger guns as taps, & found the pressure on the pumps we had tried was simply too high, making the simple task of putting water into a saucepan difficult due to the 'splashback'. So we changed again, this time to a 3.5lpm pump, a 'mid priced ebay cheapie'. Didn't help with the splashback much (they all seem to run at 35psi or thereabouts), but we have fixed that issue with a change to normal taps. The advantage of the 3.5lpm pump though is that we waste less water. It still pumps through the filter just fine, & gives plenty of flow for a shower if we want, but we just tend to use less water, which we consider to be quite an advantage. I've carried the shurflo as a spare, only because I thought the ebay cheapie may not last, but it has now given 3 years service without a hiccup. All would manage the job of filling a bladder from a bucket. Higher flow rate will just be a bit quicker. For filling only a submersible pump may be the easiest to use solution & one like
this would be quick.
Finally, back to water. We do carry a small quantity of liquid pool chlorine to use in our tanks if we have any doubt about the quality of the water (& never use cloudy water). It is really cheap to buy & we only carry 250mls, which is enough for a year or two. It does become less effective over time, but as it ages we simply add a bit more when using it. Most pool chlorine is around 12% strength. At that strength the recommended quantity for drinking water is 4mls per 100 litres. Alternatively you can use household bleach (no fragrance) which is about 1/3rd to 1/2 the strength of pool chlorine (same stuff) by icreasing the quantity. We have lived for several decades on tank water & really dislike the taste of chlorine in our water. Thankfully the carbon filters do a great job of totally removing the taste.
EDIT: B.E.S.T filters do have a 1 micron membrane at each end of the filter & thus claim that they protect from E.Coli, Giardia & Cryptospiridium. However many other 'caravan filters' are only 5 micron & don't.
