Dehumidifier Water Recycler




Introduction: Dehumidifier Water Recycler

If you live where dehumidifiers are essential to your home living, you might be interested in using the water automatically for something such as a toilet, which I've done here. You can also collect other water such as snow, shower water, etc. and add it directly to the blue reservoir. This can be valuable if you live in an area where water conservation is important.

When the toilet is flushing, a pump is activated to transfer the water from the reservoir to the toilet tank until the tank is full. This set-up can also be used to fill a toilet by gravity with a valve, but I've not found an affordable suitable valve yet. Compared to the many other powered devices you likely have on constantly at home, this system uses a very small fraction (a power analysis is provided at the last step).

The toilet water supply is adjusted to a trickle so that it has a minor contribution to the toilet and acts as a back-up when the reservoir runs low.

Step 1: Gather Materials

Because every location is different, use this list to give you a sense of what's needed.

1. Toilet with a tank that has a float attached with a metal rod to a water intake pipe

2. Dehumidifier that self-drains or has a reservoir you can easily drill a hole through the bottom of

3. Large plastic bin (at least several gallons) that will fit the location where you'll set it up

4. Shelving so that you can drain the dehumidifier by gravity into the bin (and, if desired, raise the bin so you can feed the toilet by gravity)

5. Sufficient PVC piping and connectors, mostly 1/2" diameter with some 3/4" and 1"

6. Sparky's Widgets ISRelay 5VDC-to-120VAC optoisolator relay

7. Magnetic switch (normally open) with attached wires

8. Fountain pump that can lift at least 4 feet (e.g. Beckett 7206510)

9. Tubing for the pump to expel the water through

10. 120V electrical outlet

11. Breadboard with power pack to convert 120VAC to 5VDC power for relay

12. Assorted thin wires, LED, 330 ohm resistor

13. Romex heavy electrical wire

14. Housing for optoisolator relay

15. 1" diamond-tipped hole saw

16. Finish nail 2-3" long

Step 2: Drill Two Holes in Toilet Tank Lid

For this step, you can drill holes in the porcelain lid or use a temporary lid (plastic or wood) if you don't want to modify the toilet.

For the first hole, use the 1" hole saw to carefully drill the hole (porcelain lid should be on a flat soft surface) where it would be over the metal rod connecting the water intake pipe to the float. Take your time to let the bit do the work and spray lots of water on the porcelain to keep the bit cool. The porcelain lid may have two layers to be drilled through. This hole is for the water coming from the reservoir.

For the second hole, use the same saw bit to drill over where the float would be. This hole is for the pipe that will go up and down with the float to trigger the pump.

Step 3: Attach Magnetic Sensor

It is possible to use a water sensor in place of this pipe-based sensor, but I chose the pipe route because it's fun to see the pipe move and I believe it would last longer than a water sensor (which should be low-cost to keep the overall project cost down) that may fail prematurely due to leaks or corrosion.

Take a 3" section of 1" PVC pipe and cut a slot (1/16" or 1/8" wider than the nail) about 2/3 of the way down. Attach the pipe to the right hole with the slot on one side facing forward. Make sure the pipe ends and slots are free of burrs and use superglue after pre-sanding around the porcelain hole with rough sandpaper.

With the glue completely dry (overnight is recommended), put a 1' or so section of 1/2" PVC pipe in the hole until it rests on the float. The float should be buoyant enough to support the pipe. If not, replacing the float is recommended. With the pipe sitting on the float, mark the 1/2" pipe about 3" above the top of the 1" pipe and cut at that mark. Cut a 1" section of 1/2" pipe and put a concave cut in one end so that it can sit on the longer 1/2" piece at 90 degrees. With PVC glue, attach the 1" piece at 90 degrees to the end of the pipe that was sitting on the float. Give this several hours to dry (because PVC glue is not normally used to glue pipe this way!).

Put the glued pipe back in to rest on the float and, with the 90-degree bend facing to one side, mark a spot on the vertical 1/2" pipe piece just below the top of the slot. Take the floating pipe out and drill a hole through at the mark snug enough for the penny nail to be hammered through (see right picture). The nail keeps the pipe from going all the way down with the float to keep the short piece of pipe from slamming onto the 1" pipe as well as give the float a chance to rise before pushing the 1/2" pipe back up.

Using double-sided tape, attach the two sides of the magnetic sensor to the 1" and 1/2" pipe pieces as shown in the picture. When the float is down, the magnet is triggered. The sensor pieces do not need to touch. If you are comfortable with electronics, you can test the sensor by using batteries, a resistor, and an LED in series. The sensor (normally open) closes when the magnets are near each other.

Step 4: Set Up a Location

Pick a spot where you can set up the reservoir and dehumidifier. The dehumidifier should be able to take in and release air unimpeded so a room can be kept dry. The reservoir should be able to stand without tipping over and without blocking any doors. The shelving should also be able to support a reservoir full of water (8.3 lb per gallon plus weight of reservoir). The shelving should be situated so that a length of 1/2" pipe or tubing can be run to the toilet tank, even if it is through a wall.

Set up the shelving so the bottom of the dehumidifier is at or above the top of the reservoir.

Step 5: Add Drain Tube to Dehumidifier Tank

This step will allow the dehumidifier to drain immediately into the reservoir so there is no stagnant water in the tank.

If your dehumidifier has its own drain and if you can direct it into the reservoir, that will save you some trouble. Otherwise, modifying the tank as below is needed.

This may take some trial and error to find the right combination of tank and tube that won't leak. In my case, my tank plastic seemed to be PVC so after drilling a 1/2" hole at the bottom, I was able to use PVC glue to secure flexible PVC tubing. Superglue or other strong compatible glue should also work for other materials, but don't use regular bathroom caulk because it's not designed to be in continuous contact with water (the caulk used for aquariums should be good). Put the other end of the drain tube into the reservoir. Test by pouring water into the tank and ensuring no leaks are around the drilled hole. Dry and add more glue if necessary.

Note: The white area of the tank front is covering an old hole and a messy PVC glue job. The mechanism at the left of the tank is from when I used a float to sense when the tank had enough water to pump out without the external reservoir.

Step 6: Set Up Transfer Lines to Toilet

This step will depend a lot on your room and toilet configuration, but hopefully the pictures make it clear what needs to be done.

Attach a tube to the fountain pump and put the pump into the reservoir. Plug in the pump to verify it pushes out water. As my pictures show, I drilled a hole through the bathroom wall and put the tube through and into a 3/4" PVC pipe on the other side. The pipe was connected to 1/2" pipe with adapters and run around the bathroom wall to end in a 90-degree elbow that directed the water into the tank. The pipe was supported on the wall with drywall screws that also ensured there was a slight downward slope in the pipe. All the pieces were connected with PVC glue to prevent leaks. A screw quick-release was installed near the pump tubing end so the pieces receiving the pumped water could be disconnected for troubleshooting.

An overflow tube was attached to the reservoir at a height just before the reservoir would get too heavy for the shelf. A 3/4" hole was drilled into the reservoir and a threaded PVC connector was installed, using pipe tape to prevent leaks. 1/2" PVC pipes and connectors direct the overflow to a drain in the floor.


In the first figure, there is a short pipe sticking out of the reservoir bottom - this is reserved for when I find an affordable valve to allow the water to drain out by gravity. The valve must be instant-action (not diaphragm) because there may not be enough pressure to push against a diaphragm. A piece of the gravity-fed line in the wall is also showing at the bottom of the second figure. The thick black U-shaped wire at the top of the first picture is the power line for the pump. Other wires are for the electronics.

Step 7: Set Up Electronics

It will be very helpful in this step that you are comfortable with household electrical wiring or have someone knowledgeable help you. The picture shows:

- a plug at the lower left where the pump is connected (pump outlet)

- a breadboard at the lower right for powering the relay

- the relay in the upper right box (which is normally covered)

- a blue box at the top to protect the connections (with standard electrical connectors) for the 120V lines going between the relay, a wall outlet, and the pump outlet

The schematic shows all the connections. The trigger from the toilet consists of the two wires from the magnetic sensor going to the breadboard and connecting to 5V and the relay trigger. When the magnetic sensor closes while the float is down during a toilet flush, the relay is activated to connect 120V to the pump to turn it on. The LED is on while the pump is working so you can verify the electronics are working.

You may be concerned about the amount of power used. Aside from the mandatory dehumidifier (use Energy Star if possible), the system uses 0.04 amp to feed the breadboard power pack regardless of pump operation and 0.09 amps goes to the pump when it's on. Compared to the numerous other devices such as fridges that go on in cycles, cell phone chargers (0.03 amp when not charging, 0.09 amp when charging), aquarium pumps (0.09 amp), etc. this water recycling system is comparable to if not lower than many devices on a majority of the time. However, I see an opportunity to use the toilet to mechanically switch on the breadboard, but need to find a way to do it safely.

Step 8: Run Your New System!

It may take a few adjustments to get everything to work right, but you'll have a big grin when you see how potentially wasted water (and snow!) can be reused for your toilet or other thing that doesn't need perfectly clean water.

Leaks are bound to happen, but they are easy to control with pipe tape and glue. If it's just a few drops a day that I have a hard time preventing, big deal, I just put a tray under the spot and pour it back into the reservoir.

What's great about this is that there are opportunities to make this use nearly zero house electricity or solar energy. As mentioned, there may be a way to power the breadboard only when the toilet float is down (the breadboard power pack uses a tiny amount regardless of what else is happening). There obviously are lower energy power supplies out there that I'm overlooking. If you have household solar or even set up a dedicated solar panel with its own compatible pump, you'll be able do this off-grid.

With the 15-gallon reservoir, I don't expect to empty the reservoir quickly under current usage patterns - if that becomes an issue, we'll have to implement a way to shut off the pump when the water is too low.

As mentioned in a prior step, a way to show how many gallons is reused will help demonstrate the system's usefulness - suggestions for a monitor are welcome!

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    4 Discussions


    4 years ago on Introduction

    Early on in the use of this set-up, I realized the dehumidifier wasn't going to dry a room thoroughly while in the corner. I moved the dehumidifier to the center of the room and currently pour the water from a second dehumidifier into the tank. A little bit of labor, but I've already saved many gallons of water.


    5 years ago on Introduction

    This is an interesting project, and very well documented!

    I live in a highly arid climate, so this idea is completely new to me. But it looks clever and very useful for you. About how much water do you collect in a day?


    Reply 5 years ago on Introduction

    Thanks for asking and the feedback! I'm still finishing up winter in Philly, so I fill it with snow I allow to first melt in the room. When the two dehumidifiers (one is too far from the bathroom) kick in when the humidity rises, I'll get about 5 gallons a day.


    Reply 5 years ago on Introduction

    Forgot to say that for the other dehumidifier, I'll just dump the water into the reservoir. I'll track the amount of water I use, but hope to find a flowmeter to track that.