Are there any good reasons why I shouldn't wash clothes with rainwater?

September 7, 2007 6:00 PM

Washing clothes with rain water - should I do it?

So, like a lot of Australia, Melbourne is in for a long dry summer it seems. I now have a very large water tank connected to my house, which supplies water to all the toilets, a wonderful saving on fresh tap water.

I want to hook this up to my clothes washer, already a fairly economical front loader. However, my partner and others have mentioned that you shouldn't wash clothes in tank water.

Is this true? The only potential problems I can think of would be if the water was dirty (our roof is free of leaves etc) or if it was bore water rather than rain water. Is there any good reason why I should not use rainwater for general clothes washing?

posted by tomble to home & garden (25 comments total)

I don't think rain water is clean water.
posted by fandango_matt at 6:01 PM on September 7, 2007

Bacteria, insects, other animals, dirt... It will be dirty if it is running off of your roof unless your roof is routinely sterilized.

I would personally only use potable (or near potable) water for washing clothes.
posted by unccivil at 6:10 PM on September 7, 2007

If it's captured as runoff from your roof, as you seem to suggest, you need to take into account what your roof is made of and the chemicals/elements that will be washed or leeched off of it and into the captured rainwater. For instance, the shingles on our house are asphalt, which has lead in it, and so we can't use the runoff to water vegetables without filtering it. Whatever the water picks up as it runs over your roof will also interact with detergents in various ways, too.
posted by cocoagirl at 6:11 PM on September 7, 2007

Acid rain? Or other pollution?
posted by IndigoRain at 6:12 PM on September 7, 2007

Rain water is perfect for laundry. It is very soft water. We used it for years and years. If the container that you catch the rainfall in is clean there is nothing better for washing clothes.
posted by JayRwv at 6:12 PM on September 7, 2007

Also, the average washer uses between 40 & 50 gallons per wash. Very efficient machines use between 25-30. How big is your big tank and how efficient is your washer?
posted by unccivil at 6:14 PM on September 7, 2007

For more clarification, it is a new, plastic water tank, with a mesh filter to stop junk getting in it. The roof is not near any tall trees so we have very few leaves on the roof.

Also, the roof and guttering is quite new Colorbond, so the water is not travelling over old mossy tiles and filtering through a decade of old leaf mulch, or anything like that.
posted by tomble at 6:16 PM on September 7, 2007

From the ColorBond website:

"Areas not washed by rainwater should be hosed down at least every six months (more frequently in areas with industrial fallout or high salt concentrations)."

I would be a little concerned about what the rainwater is washing off.
posted by unccivil at 6:24 PM on September 7, 2007

Sitting in the tank, IMO, will cause any silt to settle to the bottom of the tank, and you will get very clear, clean water. Really, the stuff that comes through our pipes is the same thing with the added benefit of fish poo, cow poo and chlorine. Take a jar of rainwater, compare it's clarity to tap water. I doubt you will see any significant difference.

I drank and washed in tank water for a long time in the past, and I'm hooking our tank up to our washing machine in the next week or so, as well. The grey water goes on my garden as it is, so I'll get double usage out of it. Pretty important as we're nearly at level 6 water restrictions. We're currently on 140L per person per day and that's hard enough to do.
posted by b33j at 6:34 PM on September 7, 2007 [1 favorite]

I don't know much about Colorbond except what I just read on the Colorbond web site, but it seems to be safe for water collection (from the FAQ):

* Can BlueScope Steel recommend a product to be used in the collection of drinking water?
- Recently BlueScope Steel commissioned the Australian Water Quality Centre to determine if our products meet the requirements of Australian Standard AS/NZ 4020 - 1999 "Products for use in contact with drinking water". A total of 19 products (both industrial and domestic) were tested and passed the standard. These results have allowed BlueScope Steel to confidently recommend the use of COLORBOND® steel and ZINCALUME® steel for the collection of drinking water.

If it were me, I'd feel more comfortable looking at the MSDS for it and figuring out myself what exactly it's made of and coated with. But I guess we're only talking clothes washing water, not drinking water. The only other thing I would take into account is how reversible your system is if you find the water is not doing the job you'd like it to do. That is, will you have sunk $5k into plumbing to get the water from tank to washing machine, and then have dirty whites? Perhaps a few test runs.
posted by cocoagirl at 6:44 PM on September 7, 2007

Oh good Lord, wash away. Any minor dirty in the rainwater is going the way of the other dirt in that big surfactant soup. This is a perfect use for collected water. Tell the doubters to ....
posted by caddis at 6:54 PM on September 7, 2007

After reading the above answers, I feel like I'm missing something. Why wouldn't you wash your clothes in rainwater? Barring you living in some kind of industrial fallout zone, or your rainwater somehow collecting bizarre heavy metals or something while it sits, I see no reason why you need to waste human-quality drinking water washing your jeans when you have rainwater just sitting there. It's not like you're asking if you can drink it.
posted by thehmsbeagle at 7:06 PM on September 7, 2007

Think carefully about washing dishtowels in it, but otherwise ... if it's clean, it's clean. Where does everyone think tap water comes from, anyway?
posted by eritain at 7:23 PM on September 7, 2007

What is bore water?
posted by mccxxiii at 7:28 PM on September 7, 2007

Bore water is from under the ground - you sink a bore to get it. It's often "hard" which makes it difficult to get any sudsy action happening.
posted by b33j at 7:30 PM on September 7, 2007

Places like Bermuda all the fresh water people use is rain water. If you were drinking it ideally one would divert the first few gallons of water (referred to as first flushing) away from your cistern to get rid of any accumulated airborne contaminates that landed on your roof. However for washing, unless you suspect a serious particulate concern, it'll be fine. Hanging your clothes to dry on the line probably contaminates the cloth more than the water from your metal roof.
posted by Mitheral at 7:36 PM on September 7, 2007

I have a friend who uses rainwater for everything. She has a device in her system that collects the first few minutes' worth of rainwater in a separate tank, so that the roof is washed off before the water starts getting diverted to the cistern.

She waters her garden with that roof-rinsing water, I think. But she's more concerned about birdshit than toxins.
posted by bink at 8:22 PM on September 7, 2007

...um, like Mitheral just said, the first flushing thing.
posted by bink at 8:24 PM on September 7, 2007

Another vote for- it's fine as long as your collection mechanism is clean.

"Have you ever wondered why I only drink distilled water and rainwater, and only pure grain alcohol? Have you ever heard of fluoridation? Do you realize that fluoridation is the most monstrously conceived and dangerous communist plot we have ever had to face?" - Gen. Jack D. Ripper, Dr. Strangelove
posted by JMOZ at 8:32 PM on September 7, 2007

go for it! as caddis said, you are also using soap, which will take care of any stray yuckies.

in the virgin islands, there's no public water system, so my folks use rainwater for everything, including drinking and washing. the only caveat is that the water is very soft, so you have to be careful not to use -too much- soap. but i've never had any problems with my clothes whenever i visited.
posted by thinkingwoman at 8:36 PM on September 7, 2007

Still another vote for...I'm with 'unccivil', though, in that you need to consider water supply versus machine efficiency....good luck!
posted by Womanscientist at 8:42 PM on September 7, 2007

We've only just moved back into town and town water supply after 4 years on tank water. We used it for everything, including drinking, and it was fine for us. I can't think of any reason not to use it for washing.

You don't mention the size of your tank but this page on rainwater harvesting in NZ says "a rain water collection tank which holds 4,420 litres (1,000 gallons) [is] enough to supply water for an average family use of toilets, laundry, and water for the garden (i.e. non-potable outlets.)
posted by slightlybewildered at 1:37 AM on September 8, 2007

Another vote to go for it, cocoagirl's concern about anything unusual in the runoff interacting oddly with detergent is probably the worst thing that could happen; I've only seen this kind of interaction with certain borehole water, where soap made it go blue-green. Normal rainwater is lovely, lovely stuff, just remember that you won't need to use quite as much detergent because it's softer than most tap water (and save more money! bargain!).
posted by Lebannen at 3:51 AM on September 8, 2007

Excellent, thanks all! I'll definitely go ahead with it. For interest's sake, I have two tanks, one at 4,800L and another at 4,500L. Flushing toilets for a week has barely lowered the level of the 4800 litre tank (and I have two houseguests at the moment!).

This is going to make me feel a lot happier about water usage during the predicted dry summer that is coming.

A final note for those considering hooking up the cisterns on their toilets, I went for a low tech solution - each cistern now has two lines going into it, a mains and a pump line. When I want to switch, I turn off one and turn on the other. I have to keep an eye on the water level in the tank, but this works very well and was pretty cheap to have installed.

I theoretically can reduce mains water usage to that used for showers, dish washing, cooking and drinking. Excellent!
posted by tomble at 7:46 AM on September 8, 2007

Wash your hair with it! The difference is glorious!!
posted by mu~ha~ha~ha~har at 6:49 PM on September 8, 2007