Gray Water Systems: Good Idea or Bad Mistake?

By Carl Seville, Networx

Most of us realize that water is a scarce resource and are looking for ways to use less of it in our homes. We need water to drink, for cooking, cleaning, flushing toilets, and (unless we are into xeriscaping) irrigation.  We can save water by using more efficient fixtures, taking shorter showers, fixing leaks, and being more careful about how we use it.  We can reuse water by capturing both rainwater, and gray water – the stuff that goes down the drains in our bathroom sinks, showers, tubs, and washing machines.

It is possible to clean and filter gray water and then reuse it, both inside our homes and for irrigation, but it takes effort to do it right and it comes with challenges.  First, we need to distinguish gray water from black water, which is the waste from kitchen sinks, dishwashers, and toilets.  Black water can’t be reused in our homes until it is fully treated and sanitized in a sewage treatment plant, something that most of us don’t have in our backyards. Gray water is easier to prepare for reuse, most commonly in indoor storage tanks designed just for this purpose.

Installing a gray water system in your house requires two sets of drain lines, one for the gray water and one for the black water. All the black water goes into the sewer or septic tank, and rest goes into the gray water tank.  This tank, usually in the basement or crawlspace, filters, treats and stores the gray water until it is reused. Filters take out the big yucky stuff – hair, lint, etc.

Treatment is necessary to keep the water from getting toxic, and is done with chlorine, ultraviolet light, or a combination of these and other methods.  Treated gray water can be used to flush toilets and for irrigation, under certain conditions.  If you want to use it to flush toilets, you need to have supply lines to each toilet that are separate from the regular water in the house – easy if you’re building a new house, more work on an existing home.  Gray water can be used for underground or soaker hoses, but it shouldn’t be used to supply sprinkler heads because it can spray nasty stuff in the air, in a process referred to as “aerosolizing,” that you could breathe in and make you sick.

If you decide to put a gray water system in your house, make sure you understand exactly how much maintenance it needs, and what chemicals or other treatment the water needs.  If you’re not the kind of person who likes to take care of things, think hard before you give it a try.  Filters can get clogged, pumps can break, chemicals can go out of balance – there are lots of complicated things that can go wrong with a gray water system.

Although they are allowed in many places (for instance, Arizona laws make it fairly easy for Phoenix plumbers to install gray water systems), many plumbing professionals are not big fans of gray water systems because of the maintenance and health issues involved in using them.  If you want simple, safe ways to save water, install high efficiency fixtures, take shorter showers, don’t run water unnecessarily, and put in drought resistant plants. If you want to collect water, stick a few rain barrels on your downspouts.  They are cheaper, will collect a lot of water, and you can use it for irrigation and even flushing toilets if you want, without the complicated treatment gray water requires.


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Semo K
Semo K1 years ago

Water tanks are usually made of either plastic, fiberglass, concrete, stone, or steel. And, standing water can create sediment on floors of this material. Cleaning a water tank is necessary if inspections reveals sediment has developed on the floors and walls. Some states require the inspection of and cleaning of the reservoir once a year. The sediment in the reservoir can contain bacteria, protozoa, or viruses. This can cause contamination, or, a bad taste or smell. Plus, the accumulation of sediment can create larger problems.
cleaning water tanks in jeddah

Jospeh R.
Jospeh R.3 years ago

It’s my fortune to go to at this blog and realize out my required stuff that is also in the quality. adept cheltenham

Warren Webber
Warren Webber4 years ago

Live long and prosper

jane a.
jane A6 years ago

I live in an area where we only have septic systems, which are delicate indeed. Graywater helps prolong the life of the septic, and I have it coming into areas of the property where normally I would have sprinklers. A win-win situation!

Angie B.
Angela B6 years ago

Now that the last of my brood of 7 has moved out, I find I barely use water at all. I collect rain water for the garden to drink.

Michael C.
Michael C6 years ago

Lauren W, Using the wash water is not a problem, but if your type of detergent is a type that will to be utilized directing by the plants, all the better. Other wise, many detergents must be broken down before offering themselves as a nutrient.

Lauren Weinstock
Lauren Weinstock6 years ago

I enjoyed reading the comments. I too have been watering the veggie garden and a few flowers during this drought with washtub water. My plants respond beautifully to this. Seems like it should be a little easier to collect grey water than proposed in article.

Belle W.
Belle W6 years ago

I haven't heard of it termed "black water" before, but of course it makes sense to have different pipes. I collect the cold water that comes out before my shower runs hot and use that to fill the toilet tank, which is convenient enough, but otherwise I still believe in homeowners and businesses using greywater.

Mandi A.
Mandi A6 years ago

Thank you

Donna M.
Donna M6 years ago

I don't know about this but it sounds kind of one sided to me. I don't know that you need chemicals for graywater. I use the water from my bath and kitchen to water my garden and so far have seen no negative effects. It is not a huge amount of water saved but in this drought we are experiencing every little bit helps. I would like to find out more.