purify water in tanks

[thinwater]

Originally Posted by wholybee

"Standards" are difficult to find unless you have the connections and/or money for them.
In an earlier post I posted what the CDC has to say. Here is an extensive study by the WHO.
https://www.who.int/publications/i/item/9789241509947

tldr;
The best are ultra filtration, flocculant-disinfectant, and UV disinfectant.
Not as good but acceptable are products based on Chlorine. Chlorine products do not protect against Cryptosporidium but work well on bacteria and viruses.
Ineffective are products based on sliver. These products are _partially_ effective on bacteria, and not effective at all on viruses or Cryptosporidium.

Interesting study. Thanks.


Yes, there is no one magic bullet. It takes multiple steps.


In fact, standards for public water treatment are not hard to find, because they are for public water treatment. AFAIK, the ONLY accepted chemistry for public water supplies in the US is chlorine (with other steps for cysts). Other chemistries, such as peroxide, have been studied, but they have not been accepted. Other technologies for point-of-use (not in the tank)have been approved, but curiously, RO/desal is not among them (potential for membrane leaks).



Curious, and I have searched. Peroxide/silver has been approved in a few small cases outside the US, but no national standard that I am aware of. If so, I would LOVE to see the standard and be able to share it.

[sailorboy1]

Lots of boaters in this thread should clean their water tanks because if I was concerned my tanks had this stuff needing these filters I wouldn't even wash my hands with it.

Safe water treatment protocols have been around for, well a long time. Read up on them in a real authority, not a boat forum, and just do it. Bleach is cheap and chlorine testing equipment is also cheap so you can measure what you are doing to have enough to treat the water, but so much it is going to corrode everything (if it applies).

[s/v Jedi]

Yes, the Seagull IV filter elements are high flow rate but do block all the virusses. They are also $100+ for just the filter element and another $700 for the filter housing.

[NPCampbell]

Originally Posted by wholybee

Lifestraw is 0.02 micron, and they provide 3rd party lab results proving performance to EPA and WHO requirements. I would suggest anyone considering a filter ask for those documents from any prospective supplier, and not just take their word on it.

There are other technologies though, with a larger pore size for better flow, and lots of twisting and turning so smaller particles get trapped. More expensive to produce, but reasonable flow rates. The lifestraw is quite slow, and couldn't possibly be connected to a tap or run under any more pressure than gravity feed.

Lifestraw has a bunch of filter products. The "straw" style filters have .2 micron filters and don't block viruses. According to their web site, only 2 gravity filters, the "mission" and "family" will block viruses. I believe those are the ones with the .02 micron filters.

[CarlF]

I have never heard of a recreational boat stainless water tank failing from chlorinated water. They die first from crevice corrosion - usually at the mounting pads and tie downs where moisture is trapped against the stainless wall of the tank with no oxygen. It can perforate in less than 10 years. Have a stainless lip welded so that the thin tank side metal is held 1” above anything damp.

[Ballsnall]

Originally Posted by CarlF

I have never heard of a recreational boat stainless water tank failing from chlorinated water.

Exactly, and every boat in every marina in most countries around the world will have chlorinated water in their tanks. It's the cheapest, easiest and most effective method.