DIY Solenoid ATO (Auto Top Off)

So after looking around, and seeing what I had on hand I decided to DIY an ATO.

Step one: Redundant float valve assembly. $10
Float valves, already had one, other was $10 at Graingers. Screwed them onto a heat formed acrylic mount, tapped with a 1/8" NPT tap. I could have made one mount, but my original plans called for one valve on each end of the sump.... for some silly reason I've already forgotten. They're mounted in a NO (Normally Open) configuration in serial.


Step 2: Build valve assembly. $22
I used a 24v Toro 3/4" sprinkler valve, $12 at Home Repot. I built a 3/4" to 1/4" quick connect poly adapter. Each end was around $5, uses 3/4" F-F threaded coupler, a 3/4 - 1/2" PVC reducer and the 1/2" to 1/4" quick connect reducer. The valve is mounted to a piece of scrap wood w/ screw-mountable zip-ties which is in turn mounted to the outside of my stand so it's easy to check for leaks and such.


Step 3: Triple redundancy and power $0
I installed a 24V AC "wall wart" to a timer that turns on for a total of about 90 minutes a day. Only during on cycles can the tank fill. If for some crazy reason BOTH floats failed closed then I would at least limit the water on the floor, if not save the fishies. I had the transformer and timer aleady from past projects. This set up also prevents premature wear on the valve as it will clearly define an "on" and "off" period where minor fluctuations in water level wont false trigger the valve to open for a split second. these valves have a response time of a few milliseconds, no need to make it click all day.


Step 4: Install and test.
I used gel CA glue to mount the floats. Wired them up with weather proof wire nuts, and hooked up the water. Checked the floats and valve, all worked like a charm. I guestimated the "open" point on the floats and got it pretty close. It keeps the water level within about 1cm of this picture.


Total cost of new parts: $32
Total estimate cost of parts-on-hand: $30
Time: 2 hours.

Thanks for looking, always open to suggestions/comments!

-Doug

 

very good diy! k+ to ya!

 

Awesome. I have been searching for a ATO DIY and I just found it. Thank You..
k+ on the write up

 

Nice job, man!

Looking more at the pics, if I could make a suggestion. Very minor, but one the 3 wire nuts mounted just above the solenoid is situated horizontally. The other two are vertical, which is good. You might consider using a cable tie and shoring all 3 together just below the skirt of the wirenuts. This will keep all 3 vertical--and even though you used weatheproof nuts--vertical is a good habit; especially around water.

Again, nice work.

 

That's pretty sweet soul.
K+ on the DIY!

 

Looks great!!! I have a very similar system on a fountain in my back garden. Be careful with that sprinkler valve--I had one not close all the way and flooded my back yard. I know you have the timer set for 90 min, but alot of water can run in that amount of time.

 

I hear you on the valves going bad.... I've used many of them for irrigation, and they're not perfect. Most failures I've seen on them are a result of foreign matter in the diaphragm, not a problem after 6 stages of filtering. My next upgrade will be a second redundant valve. I'm not sure if I want it NO or NC, and how i will wire it... I have 4 variations on the theme in my head, running scenarios in my sleep... NO would require it to pull current 24/7, NC would be hard to plumb, as the second in line would have very little back pressure which they require to close fully... it means I'd have to make a delay... *shrug* for now I just check it daily. A valve that fails rarely fails full open, so a constant but slow drip would be apparent in raised water level in the sump before any disaster... *knock on wood*.

As for the timer, the max flow from my 100gpd R/O that runs on the slow side would be 6.25 gallons in 90 minutes. Not enough to kill anything... but a moot point should a valve fail open. The current holds it open, the timer stops current. A failure wouldn't require any power, it would just be open.

...also... I've seen people claim that the Madison float switches aren't rated for submerged applications. I need to pull these out and re-do their leads with some tubing and silicone I think.

Still in the works I guess

-Doug