Hydroponics Float Valve




About: Software engineer, using electronics and micro controllers as a hobby to keep me sane!

Do you want to keep your reservoir topped up without hassle?
Don't want to buy an expensive float valve?

Make your own!

I have been building a hydroponics garden, and I wanted to make sure my reservoir doesn't run dry and destroy my pump (or kill my plants), but a side entry float valve would have cost me $30+ at the local hardware store, and I had already spent my budget on pipes and plants.

So, calling on my childhood obsession over MacGyver, I looked for what I had lying around, and built a cheap and surprisingly effective float valve! (effectively for free!)

Step 1: Disassemble

Start with opening up the sprayer.

If you look at the spray end, you should notice it looks like an inverse nut.
Push your pliers into the corners, and turn like a screw, it isn't hard to get undone.

When you have the front off, unscrew the small plastic nut from the other end, and slide out the innards.

Step 2: Mod and Reassemble

See that spring?

That is the one thing holding us back (it is way to stiff, and we don't need it!).
Simply slide it off.

Now, without the spring, there is nothing holding the plastic shaft to the handle, the shaft will happily go in to the open position, as the nut is pushed up by the handle, but it won't push back in.

I found a small rubber thing (picture 2) laying around, so I drilled a hole in the centre, and used a grinding bit on my dremel like tool to make it shorter.

This fit perfectly on the shaft before the handle (it actually 'screwed' on!).

Now when the handle goes down, it pushes on this bit of rubber and the shaft goes in as expected.

Step 3: Add the Weight / Float

Drill a hole in the sprayer handle (black handle). Put a bit of stiff wire (I used a bit of wire from a metal coat hanger) through, and bend it to wrap around the handle.

The rest of the wire should be wrapped around the neck of a water bottle.

Put enough water in the bottle to pull down the handle, leaving enough air to push the handle up via buoyancy.

Now just attach your contraption to your larger water barrel, drop the float into your reservoir, firmly attach the sprayer and you are done!

When the water level drops, so will the bottle, pulling the handle down.

When there is enough water in the reservoir, the bottle will float, pushing the handle up, and closing the sprayer.



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    11 Discussions


    2 years ago

    This is effing brilliant. So simple :)

    Yep, except that would cost money, I had the hose attachment come with the hose I used for the system, so it was basically free! Also you need to get a specific toilet float valve, one that fills from the side, instead of the more common filling from the bottom.


    10 years ago on Step 3

    Killer idea and execution. I just build an auto top off using a toilet ballcock kit. It works well but is very slow to fill. I wish i had found this first. I'm gonna build it any way. Thanks!


    10 years ago on Step 3

    The purpose of this is a bit confusing to me. Why not just use a larger bucket? I had a similar setup with a 18 gal. Rubbermaid container for the reservoir. I like your solution for the screens. That was the one problem I had was that the roots clogged the hose and flooded the top tube and dried out all the others. Killed the whole crop. Great instructable!


    10 years ago on Introduction

    nifty indeed...i've seen people use toilet parts for this kind of thing...which are easy to acquire

    1 reply