We have approx. 1,000-gallons rain water storage in a variety of containers that range from 50-gallon, 165-gallon and 215-gallon. It's used for outdoor watering (garden, grass and landscape). I wouldn't use it for laundry unless it was our only choice, and then I'd purify it some way - probably solar distillation - before using it in the laundry. At the very least, I'd filter it (and there's a big difference between purifying and filtering) first.

There are a large range of contaminents you are introducing into your wash water from leaves, dust and chemicals that settle on the shingles from the environment, bird droppings, the gravel from tar or asbestos shingles, lead from gutters that may have been painted with lead paint (if they are old gutters), etc. If you have treated cedar shake shingles, it's not advised to use catchment water off that type of roof at all.

We clean our barrels several times a year and scrub them out with soda and water. They are closed containment, other than the 3/4-inch hose to the rain diverter. We also have a Gutter Helmet over the gutters to prevent the "big stuff" from getting into our barrels.

-Grainlady

Good point! My yard is entirely organic, and my household products are all biodegradable and non-toxic, etc. (I have a septic tank, so I try to keep everything natural.) And I roll in dirt and play with bugs anyhow, so everything around my house comes into contact with my clothing. So any rainwater that isn't downright brown is probably cleaner than my gardening clothes.
Also, I count on the clean water of the rinse cycle and the surfactants in my detergent to sweep all that grunge down the drain.
So for myself, I don't worry about any pathogens or contaminants -- I'm good friends with them all. But for someone with a compromised immune system, it's probably best to heed your caution.
And good, good, good for you for using rainwater in your gardens!!!

In my cellar I still have the original rain water cistern for my 1840's house. I think it's about 1000+ gallons. After the first years or so we stopped using it, though up until then, I used it in my FL washing machines and toilets without filtering and with no problems. It does require some management and choice about which rainfall and when during the storm to open the diverter so it flows into the cistern.

Lately I have been thinking about replumbing my system so I collect washing machine outflow (grey water) and store it in the cistern and use it for flushing the toilets. I just haven't gotten around to making plans for the switch. It would be neat, though, to use the same water twice: once to wash and once to flush.

In my area rainwater is quite soft so washing with it is very nice. Since I have FL washing machines that don't need heated water (they make their own heat), it was easy to have a cold-water only circuit that fed the toilets and the washing machines.

Molly~

Yay for you, Molly, for recycling water! Wow, an 1840 cistern!
Be careful about storing greywater, though... I think if the water sits around, it will get slimy and icky. I've heard that greywater should be routed through an outdoor biological filter... pebbles, sand, water plants, some snails maybe... something along those lines... to keep it fresh. The little microcritters eat up all the fungi, algae, and other scummies.