DIY Auto-Top off with Solenoid

[Zephrant]

Here is a quick run-down on building an auto-topoff system, that utilizes a float switch and an AC solenoid. This is designed to be used in a sump of any kind. In my case, I had an internal baffle that I could install the switch in, that did not need to be water tight. This switch can also be screwed in to a ½� bulkhead directly through the wall of the sump if desired.

Tools needed:

• Drill
• 1/2" NPT Tap
• 3/4" Forstner bit
• Soldering Iron, solder, flux, heat shrink tube

First, go to www.mcmaster.com and order a Polypropylene solenoid- Part 7877K53, for $18.12 each.

While you are there, order an AC float switch- Part 46515K41, $15.13 each.

Hit Home Depot and pick up a pair of 1/8�NPT to ¼� Speed-Fit adapters for $1.50 each. Using Teflon tape, screw then in to the solenoid.



Acquire a two prong power cord, or some cord and a plug as needed. If you have to cut it off of a lamp in the front room, unplug the lamp first… and mention to the wife that you think the bulb is burned out in your way back downstairs.

Ok, get out the soldering iron, and heat shrink tube, we are going to work.



Cut the wires off even, and strip 1/4� off of all ends. Put a little electrical flux on each wire, and apply the iron with some solder (this is tinning the wire).



Slip a 1/2" piece of heat shrink tube over the wires as shown. Slip a larger piece over the AC cord too. Now here is the tricky part: Using a vise, or your hands, hold the two wires end-to-end, so the 1/4" tinned part overlaps. Touch it with the iron for a second, then hold them together until they cool. Done right, this takes only a second, and the joint is clean, and shiny.



Wire up as follows- The AC power cord has two wires. One goes to the float switch (white wires), the other goes to the solenoid (red wires). It does not matter which of the white or red wires attaches to the AC cord. That leaves one white wire from the float switch, and one red wire from the solenoid unattached, so attach them together. Only 3 solder joints, and already we are done. Slip the heat shrink over each joint, and heat with a heat gun. Slip the large piece of heat shrink over the other joints, and shrink it down too. This will help prevent water from getting in the joint, and give it more “strain relief�. Make sure all the wire joints are fully covered. Smear some silicon on them if you are concerned they will ever contact water.



Stand back and plug it in. Flip the float switch around, and you should be able to hear the solenoid open and close. Unplug it, pat yourself on the back for not smoking anything, and lets continue.



Now comes the fun part, drilling the tank when water is in it! Lower the water level as far as possible, but at least 3� below the hole. The hole needs to be at the water level you want to keep in the sump. Keep in mind that it is not adjustable later, without re-drilling. I used a Forstner bit from Harbor Freight, but a small hole-saw would be fine too. Lay a paper towel over the water, under where you will drill, and drill away. Use a cordless drill, and keep reminding yourself that the drill is shot if you drop it in the tank! Drill slowly, and don’t press hard. When you get almost through, go even slower.



Using a 1/2" pipe thread tap, tap the hole. In my case, I was taping 3/8� acrylic, and it went in pretty easy. Make sure you use the correct tap handle for the job.



Pull out the paper towel, with the drillings on it, and chuck it. Use a net to fish out any stray plastic pieces.

From the back side, screw in the float switch. It only needs to be snug, but it does need to be right-side up. In our case, we want a float-up to be “off�, and a float-down to be “on�. Use a O-ring or two on the back side if you can’t get it snug in the right position, or if you are going for water-fastness. Use Teflon tape on the threads as well if needed.



Attach the water from the RO/DI unit to the inlet of the solenoid, and another line to the outlet. In my case, I ran the output line to the Kent mechanical float valve, which is set higher in the sump. If the solenoid ever fails open (unlikely, as it is a normally closed valve) the float switch will prevent the sump from getting too much fresh water. Mount the solenoid securely up out of the way, so it can’t ever get wet. Tie-wrap the wires out of the way.



Plug it in, turn on the RO/DI feed line, and twiddle the float by hand to make sure it comes on, and goes off as desired. Using a valve, adjust the flow to a trickle. If something fails, restricting the flow will mean you have more time to notice before you are attempting a freshwater Reef tank. Keep a close eye on it for a day or two.

Note that this is an ideal setup for a Kalk reactor too- Just put the kalk reactor after the solenoid, and don’t use the Kent float valve.



Total cost: $36 plus that stolen lamp cord.

Disclaimer: I currently believe that the above components are usable as described, and are salt-water safe. However, use at your own risk, and if you blow up anything, take pictures, but don’t go blaming me!

Zeph

[North Bay 101]

You do the best posts . I think that the moderators should change your handle to DIY Guru. Thanks for the great posts.

North Bay

[jorge]

Zephrant:

Where in the home depot do you find the Speed-Fit adapters? I have never seen them.


Jorge

[Kimo]

Zephrant,

Man, you should write a book

All of your instructions are very clear and concise, bravo.

I'm going to try this out as soon as I get my new sump.


Thanks,

Jamie

[Lunchbucket]

dang man that is NICE!! thanks for the part numbers, where to get them, price, etc. you covered EVERYTHIGN in a very easy non-DIY'er language. thanks. i am gonna pick this stuff up and use it in a rubbermaid tub so i don't flood my kitchen every damn time i make RO/DI water

Lunchbucket

[Lunchbucket]

hey buddy...i just realized i would like to install this into a cap on my 5gal water jug and would need a verticle float. there are like 10 of them at mc masters...which one should i get?

well, i ordered a vertical switch for my 5gal jug. got part number 50195K93 that should work right??

Lunchbucket

[Zephrant]

Thanks for the comments all!

Jorge- In my HD, they are in the plumbing isle with the hose, and nylon fittings. They are in little plastic bags with pink tops, hung back in a "box" unit that makes it hard to find them. They have all sorts of the speed-fittings, but rarely re-stock. My local Ace carries a few things too.

LB- That one looks perfect too. Just remember if you mount it in the top of the jug, then leave the jug cap off, that it is probably "on".

GL all-

Zeph

[Mr_Quality]

Nice piece of work!

Do you think the solenoid would be able to hold back city water pressure if it were supplied that way instead of the RO output?

[Lunchbucket]

Just remember if you mount it in the top of the jug, then leave the jug cap off, that it is probably "on".

yeah i am gonna mount it in the cap. i got a john guest union from us plastics so i can mount my water line in there too. what do you mean by leave the cap off, that it is prolly "on"??? do you mean just leave it unscrewed so the air can excape??

Jorge - i got my fittings at www.usplastics.com i needed a few other pieces for this project too so i went there...they ROCK

Lunchbucket

[jorge]

Zephrant: Thanks, I will look for them.

LB: Yes, USP carries them, but I rather get them locally. Grainger also has them, but in packs of 10 which worked for the mpt adapters, but for valves and such it becomes expensive. A 5 pack of the valves is like $50+. McMaster carries something similar, but I think it is another brand.

Jorge

[schemo]

simply awesome!!!!!!!

you rock Zeph!!!

schemo

[Jorsan]

Maybe a stupid question but, why use two devices that are doing the same thing?; if you use the kent mechanical float valve as the final guard, why not use just this device alone?; maybe Im loosing something here but please, would you let me know what is it?

[Lunchbucket]

a kent float won't stop an RO/DI unit from making water. the pressure isn't great enough IIRC. need to shut off the sileniod so you stop making water

Lunchbucket

[jarhead]

Originally posted by Lunchbucket
a kent float won't stop an RO/DI unit from making water. the pressure isn't great enough IIRC. need to shut off the sileniod so you stop making water

So if the float switch fails, how does the Kent float valve act as a back up?

[Jorsan]

Thanks Jarhead, you just post my next question.

[Zephrant]

If the float switch sticks on (think snail taking a nap), or the solenoid sticks on, the water level will rise until the kent mechanical float valve pinches off the water flow. This prevents the system from feeding the tank water 24/7 until you notice the flood.

Either system can work by itself, cascading them gives a little redundancy such that if one component fails, the whole system does not fail.

There is no fail-safe in this design for the situation where the float sticks off, or the solenoid sticks off, that was not my intent. In either of those cases, I could notice the low water level and take action before any damage was done. With a stuck-on top-off, it would be possible for it to "fill" the tank for 12-24 hours before I would notice.

Zeph

[Lunchbucket]

Zephrant - got my parts today. i have a horizontal float and a verticle float since i forgot i would need a verticle for my 5gal water jug. it works out great this way though!! now i can mount my horizontal in my 5gal bucket or a bigger rubbermaid and have it dump in there for water changes and i will still have my verticle mounted in the top of my 5 gal jug i use for top off!!

i hooked them up and they work GREAT..on a dry run. i dont' have my parts from US plastics till tomorrow!! thank GOD now i won't flood the floor anymore!

also, i attached them w/ male and female plugs so i could swith the selenoid from the verticle float to the horizontal float w/out unwiring or buying another soleniod. great idea on my part LOL

thanks again!!
keep those kick *** DIY's comming man!
Lunchbucket

[jarhead]

Zeph,
How do you have your reservoir for water changes set up?

[Zephrant]

Jarhead- I have a 5 gallon pressure tank on the RO/DI, with an automatic shutoff (all from aquaticreefsystems.com ). I have replumbed it a little. The tank holds RO only water, for use in the kitchen et all. It also feeds a DI unit, which feeds the solenoid for my tank.

So the RO unit only kicks on when the 5 gallon tank is low, and turns off when the tank is full. In reality, due to my lower water pressures in the house, the tank holds about 2 gallons. On my list is to purchase a booster pump for the RO unit, to bring the pressure up higher.

In my plans is also to make a reservoir in the fish room for water, so I have more RO/DI water sitting on hand for water changes and all. When that is in place, I can use more solenoids and switches to turn on the RO/DI feed when it is low, and off when it is full. Thus allowing the RO/DI unit to run the longest time. (On/Off cycles allow a small amounts of junk to pass though the membrane to the clean side.)

HTH

Zeph

[ddenham]

Maybe I missed it or don't understand something about RO/DI, but, with the solenoid on the outlet of the RO/DI doesn't that mean the waste is constantly flowing, 24/7? I know it's not much but it adds up doesn't it? Also I thought/read that a membrane will not last as long if there's constant pressure on it. Is that the case? Mr Quality asked if the solenoid could hold back city water pressure, did I miss the answer? This is an awesome post, thanks Zephrant. BTW You're lucky to be able to get those speedfit fittings at HD , I can't find them locally here in Philadelphia (I can't complain, we do have southdown here, though).

[Lunchbucket]

yeah the waste still flows. for me it is nice that i don't have to watch it so close..that i don't flood my kitchen. i watch it just not that much...so i won't waste much even if i do run waste w/out ro/di.

also, on the topic...could you put it in line w/ the inlet of water to have it shut off?? or would there be too much pressure etc?

Lunchbucket

[jarhead]

Originally posted by ddenham
...with the solenoid on the outlet of the RO/DI doesn't that mean the waste is constantly flowing, 24/7? I know it's not much but it adds up doesn't it? Also I thought/read that a membrane will not last as long if there's constant pressure on it...

I don't want to take this thread off topic, but my post in the Reef Discussion forum will answer your question. Pay particular attention to the reply on the 2nd page by The Gang from ARS.

[Zephrant]

DD- I have an pressure cut-off regulator on the input of the RO unit. When the good water stops coming out of the RO (due to the tank being full, and the solenoid closed) the cut-off stops the water going in to the RO/DI. No continuous running, no static pressure on the membrane. This device can be retrofit to any RO/DI unit.

I quick search of McMaster-carr reveals that the solenoid is rated for up to 150PSI. Since normal water supplies rarely go over 70psi, it should be fine.

I'll trade you some speed-fits for a few bags of southdown. I'll pay shipping on the speed-fits, if you ship the SD.

Zeph

[Nammy]

Thanks for the clear instructions. Off to Home Depot I go.

[Lunchbucket]

Zephrant - where you get that one to hold back your inlet water??

Lunchbucket