Graywater Central

Great, easy way to use graywater at home

Incorporating graywater use into your daily life is such a good idea, but sometimes it can seem so complicated. Is there an easy way to use graywater?

Fortunately, there is!

Toilet-sink combo for easy graywater use

A toilet-sink combo is a great water-saving (and space-saving!) device that lets you wash your hands with new fresh water on its way to fill the tank, so you don’t have to turn on the sink. It’s water that’s already on its way to do a job, doing another job first.

Washing up with clean water turns it into graywater, so next time around, you’re using graywater to flush the toilet.

Genius!

These are all over Japan, as you see in the video above.

For your own home, you can buy a whole new toilet from Home Depot if you want, or you can retrofit your existing toilet with a much cheaper alternative, a tank-topper sink attachment fitted to your model.

SinkTwice tank top attachment

This is the Sink Twice Original. There are several charts to match your toilet model with the appropriate size sink attachment. This is one example:

SinkTwice model chart

Another option is the Sink Again:

SinkAgain tank topper

Click through to the page and see if your toilet model fits one of the options.

This is one of the best ways to incorporate graywater use into your home. No complicated plumbing, no holes drilled through walls, no need for city permits or inspections.

Perfect!

Wash my hands with toilet water? Are you serious?

First things first: the water that comes into the toilet is drinking-quality water. It would be prohibitively expensive to plumb an entire separate municipal delivery system for a second level supply.

Second, the water that goes through the toilet starts out inside the tank. It doesn’t reach the bowl until you hit the flush lever. Here’s how a toilet works:

toilet cross section showing water levels

A toilet sitting idle has a small amount of water in the bowl. It stays there because the curved pipe inside bends back up higher than the level in the bowl.

There is also a quantity of water in the tank.

When the flush lever is pulled, water flows down from the tank into the bowl. The weight alone of this falling water pushes the water in the bowl down the pipe and over the top of the curve inside.

toilet cross section showing water flow path

The flow creates a siphon effect that pulls the rest of the water from the bowl along behind it until it’s all drained away.

Meanwhile the flapper valve inside the tank has already closed, and the tank refills once again with fresh clean water.

Fresh clean water incoming

The genius of the tank-topper mechanism is to insert a faucet into the incoming fresh water line before it fills the tank, ensuring your hands are washed by the same quality water you’d be using at the sink.

You don’t even have to turn it on. That water would be going that way whether you wash with it or not, so it flows regardless. Because there is now a faucet there, you have the option to wash your hands without running additional water at the sink.

The soapy water that washed your hands goes into the tank, ready for the next flush. It never touches you again, because its next move is to flush out the bowl next time around and go right down the drain pipe. So yes, we’re serious: Wash your hands with toilet water! Just do it with a tank-topper faucet.

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