I've been trying to think of creative ways to save on water usage, and one way I thought of was to collect graywater from showers or washing dishes to use for flushing the toilet to reduce # of flushes.

However, I have heard that there are bacteria that are beneficial to our drainage systems. Apparently Drano can be pretty harmful to that bacteria. I understand that Drano is pretty aggressive as an example, but what about the variety of shampoos, conditioners, and soaps from showers and dishwashing? Can't those be potentially harmful the normal bacteria specific to toilet drainage systems?

  • Where are you considering diverting shower and dish washing drainage from? Are you sure it's not already co-mingled? Jul 22, 2021 at 1:36
  • @Jean-PaulCalderone I intend to put some buckets in the sink and tubs to catch the water!
    – Meia
    Jul 22, 2021 at 2:46
  • 1
    That's not where you're diverting from. That's how you're diverting. Where was the water going before? Jul 22, 2021 at 9:45
  • @Jean-PaulCalderone Good point! Hm I suppose I can assume they go to the same place. 0_0
    – Meia
    Jul 22, 2021 at 21:05

2 Answers 2


Your shower water is already going into the same waste pipe that sewage from the toilet or septic system empties into. I think if you have a lot of soap you might end up with soap suds or scum inside the tank of the toilet, but I don't think that it would hurt the waste infrastructure in any way.

  • I agree, decades past some homes grey water bypassed the septic tank directly into the field but that practice is rarely used today.
    – Ed Beal
    Aug 14, 2021 at 22:12

If it's filtered. Typical things that go down the shower besides the water.

  • shed skin
  • Hair (body, pubic, head)
  • minute fecal matter if you're cleansing your....lower body.
  • Residual chemicals you maybe exposed to
  • chemicals from various hygiene/beauty products (Makeup, deodorant, body sprays, perfume, cologne)

Since greywater goes thru usually a filter stage, most large particles are taken out. However if you're concerned about that stuff going in the water, mitigate using those things. Organic waste and detritus going down the drain isn't a big deal. If anything, bacteria, etc will eat that stuff.

  • Why would it need to be filtered ? if grey water is not separated from black water it usually goes to the same place so there would be no difference just less fresh water going down the drain.
    – Ed Beal
    Aug 14, 2021 at 22:09

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