Adjustable Float Switch


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6 May 2007
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Make a simple, cheap adjustable float switch for switching on an top off pump.

1) Take a common float switch (might also be called a level reed switch, I'm not sure). The one in the picture below fitted snuggly into the 25mm PVC T-Joint. If it doesn't, you can use any strong reef safe glue to hold it in place. See picture below:


2) Take a 25mm -> 20mm reducer bush and insert it into the other end of the T-Joint. I used PVC-U from Tangit but a better known product is PVC-Weld. See picture above.

3) Join, into the reducer bush, a piece of 20mm PVC pipe. Use your discretion to judge how long it must be. See picture below.

4) Take another 25mm T-Joint and bond it to a 25mm elbow joint (90 deg.) using a small piece of 25mm PVC pipe in between. Here come a bit of trial and error. Saw the piece of PVC pipe just long enough so that the two joints fit perfectly and leave a gap slightly bigger than the thickness of glass you intend on hanging it onto. See picture below. This way the glass it will be hanging onto will fit snuggly into the (white below) gap.


5) Drill a hole for a small screw to fit into the second T-Joint as in the picture above. If you have access to Nylon screws/bolts, use that. Stainless steel should be ok to use.

6) Now, insert the pipe from 3) through the fitting you created in 4). Hang it onto your sump glass and tighten the screw at the right depth. See image below:

I use the same float switch but have never thought of putting into a pipe, gr8 idea, as it is now adjustable.
Very Neat Galibore !!!!

Nice work and thanks for sharing that with us.
Thanks guys,

BTW, anyone know where I can get Nylon/Plastic nuts bolts etc?
the only ones i know off would be like on number plate lites.cant remember name now but will find friend buiding his own becket skimmers and ca.he is using plastic screws
I've been looking everywhere. No luck.

But I do live in a complex where all the cars are not in lockup I think I'll have a little excursion tonight with a screwdriver and a flash light.
lol, you can get those plastic number plate screws from most car spare places.

I know of 2 Nut and Bolt wholesalers here in DBN that stock plastic and nylon screws. Action Bolt and Boltfix. I think they have branches in JHB as well but don't have any numbers. They should be listed though.
How easy is it to connect one of those float switches up ? And where did you get it from ?
How easy is it to connect one of those float switches up ? And where did you get it from ?

Very easy. You can get them at any electrical shop. I bought mine from LFS in my ignorance and paid way too much.
Thanks guys,

BTW, anyone know where I can get Nylon/Plastic nuts bolts etc?

Try Radio control hobby shops they use them on aircraft wings, to hold the wings down, wing bolts made from nylon so it can brake easily in case of a crash to minimise damage to the rest of the plane.
My auto topup cost me R45.00 :) got a float switch from Cosmotronix LSA-34-1/2,
used old transormer, rectifier, LM7812 and a 12V relay. And an old Resun as feed pump into airline tubing.
This is still in the mk I phase, I need to make a nice perspex frame:
The sensor is in my display tank, because the display tank is the sump of my above tank sump :)
Cosmotronix. LSA-34-1/2 Or the R/S catalogue. I have a rough sketch of how to connect if anyone is interested.
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