Okay, any number of natural (or man-made) disasters could stop the water from flowing safely from the taps and contaminate the local groundwater and streams.
But what about the rainwater?
It seems to me that many (but definitely not all) of these scenarios would leave the rainwater safer than anything already on the ground. I'm considering harvesting my roof's rainwater using a collection barrel. In case of emergency, it should require less filtering than the local creek.
In non-emergency times, I could use the barrel to water the garden, defraying the cost of the city water.

Living partway between Portland (OR) and Mt. St. Helens, I have plenty of rainwater, but if we have a repeat of the last Mt.St.Helens eruption, the ash plume would cover the roof and render the rainwater an ashy mess.

Any thoughts?

BBQ_Pork... welcome...one YouTube channel I like to watch is "LDS Prepper" and he has a pretty good rainwater collection system, but I especially like his dump system to divert the initial run off away from the collection tanks... I live in an old Florida residential community with no heavy industry, and other than lawn maintenance, not too much ground water pollution..my shallow well is 25' and that is my supply...my concern for your location is when our Chinese friends decide to test something out in Lop Nor (Lop Nur) you get a bit of it a couple of days later... not that they would test in the atmosphere..

Check these out:

Berkey Water Filters
These supposedly filter out most bacteria, virsus, cysts, heavy metals and chemicals. They come in various sizes from backpacking to the Crown model that does 26gals/hour. Note that they cannot be shipped to CA until they are certified to be lead-free. There are several US distibutors.

This site has the 'Go" model for backpacking, BOB, etc. They also have a "Sport" model which is a bottle with a straw (listed under Accessories for some reason).

Big Berkey Water Filters

I have not used one of these. And, I am not affiliated with them in any way.

They do look like nice filter systems.

Great question. What I go with is a camping type filter, but my main back-up is stored tap water.

Wow, looks like there is a lot more to my question than I realized! Lots of good information here. More research required.......

So, my dad is considering building some contraption out of PVC pipe and Brita water filters.
Now, I've read the side of the box on those things and they say nothing about filtering down to x number of microns. They do claim to remove certain metals and chemicals, IIRC.
While they make mediocre city tap water taste a lot better, I have no evidence to believe that they would make the water safe if it's not already reasonably safe.

Assuming that he still pre-filters for sand and large grit before the water pitcher filters, is he wasting his time thinking that these filters will get out all the smaller, nastier things?

BBQ_Pork...to filter out virus, you need to exclude a diameter down to about .02 micron, .1 micron for the larger bacteria ...for heavy metals and city chlorine, there are some surface bonding resin strata and activated charcoal filters available (which I assume Brita is), but they will need periodic replacing....

I chose to use a Sawyer filter (5 gal kit with the .1 micron filter) for my hurricane supplies, that can be back flushed and is good for a million gallons...and plan on using a chlorine based purifier anyway, so went with the cheaper .1 versus the .02 filter... I built a DIY vertical PVC column that I filled with aquarium grade activated charcoal, but haven't tasted it yet...

what exactly is your Dad wanting to use the filter for? good tasting water, or emergency water?

BBQ_Pork,

The Britta filters take out chlorine, mercury, lead, and copper--no biologicals. I use one at home just for it's ability to remove the chlorine taste.

Here is a comparison chart showing some of the major brands of water filters and what they remove:
Water filter comparison chart

Primarily for emergency water.


Looking at your post, I'm wondering if bacteria and viruses are going to still be a problem.
Our (mine and his) water ideas are similar, and if he is planning on harvesting from his heavily mossed and likely fungus/mold-carrying roof, he will have to be careful, in my opinion.
1) large coarse filter/screen for sand and grit
2) filters, like Brita or charcoal or such.
(store-bought filters seem like an expensive way to go, especially if we're thinking long-term or large quantities. it's just one man and a small dog, but still...?)
3) boil?
4) let cool and enjoy.

I'm thinking that boiling the water can't hurt (other than requiring fuel/energy for the fire/heat), but wondering if it is needed.

BBQ_Pork,

Take a look at one of my previous posts in this thread regarding Berkey water filters. This is what I would use as a final filtration. They are expensive upfront, but they take out just about everything for about 1.7 cents/gallon.

And no fuel required.

I am not affiliated with Berkey.