Greywater questionnaire

Considering a Greywater System? Here are some questions to ask yourself to get clarity on what will work best for you.

  1. Do you have a water softener?
  2. If so, does it use sodium or potassium chloride?  You will need to switch to potassium or un-softened water in order to send greywater into the garden and have it not damage the soil and plants.
  3. Is your home on a raised foundation (crawlspace) or a slab?


  1. How many gallons per load are used by your washer?  A typical top loader uses 30-40 gallons, a typical older model High Efficiency washer use 15-20 gal, and a new HE washer uses 8-12 gallons.

Usually the two best ways to find out how many gallons per load are either to call the manufacturer and ask them, or to physically take the discharge hose out of the standpipe and put it in a trash can and measure how much water comes out during each cycle. If you use the second method, make sure the trash can is big enough to handle the amount of water that will be discharged. Typically, the owners’ manual or online information do not tell you the gallons per load of any washer. A range is a fine answer if that is true for you, i.e. you do different size loads at different times.

  1. How many loads do you do per week?

We are looking for an average number of loads done per week. The answer should be as close as possible but does not have to be exact if it’s difficult to say or varies a lot.

  1. Is your washer located on an external wall or close to an external wall?
  2. What kinds of plants are you considering watering with laundry greywater? Are these plants level with or downhill from the top of the washer?
  3. Laundry cleaning products should not contain sodium, boron, or chlorine bleach when the greywater is sent to the garden- these elements may cause damage to plants and soil. There are excellent greywater-safe products- one invented by a Santa Barbara local is called Oasis. Are you willing to change laundry cleaning products?


  1. How many people are in the household/or who take showers or baths regularly in the bathrooms that will be used for greywater reuse?
  2. How many showers of what approximate length does each person take per week?
  3. How many baths does each person take per week?
  4. What is the capacity of your bathtub- how many gallons of water does it take to fill it to the level you bathe in?
  5. Do you have a low flow showerhead? What is the flow rate for each shower considered for greywater reuse? A low flow showerhead may be 1.5- 2.5 gpm (gallons per minute). A showerhead that is not low flow may be 3-5 gpm or even more.
  6. What kinds of plants are you considering watering with bathroom greywater? Are these plants level with or downhill from where the bathroom is located in your home?

There are many options for greywater reuse systems. Whatever your answers are, you can probably find a greywater solution that works for you and your household.