Sprinkler solenoids?

Make sure they have no brass or copper bushing in them. I use a Rainbyrd valve for my ATO at it is all plastic. You have a good ideal going on and just make sure you keep the relays in a air tight enclosure because of the corrosive atmosphere.
You might want to check flee-bay and local listing for a OM valve. I found my 7,500 gph model there and saved a ton.

 

I looked and the only thing that I saw was the stainless steel spring and rod in the middle. The relay will be somewhere else (probably in the attic, or garage or something) or will be sealed. I looked for the oceanmotion on ebay and did not find any (will look again).

 

I honestly dont think a sprinkler solenoid could handle the abuse like a OM 4way. The rubber will dissolve in the saltwater and create a lovely cyano bloom. I read a thread on RC where this kid was making a replica out of machine wax (similar to plastic).

IMO, if you want something like the OM 4way and that can handle what the OM 4wy does, I would just save my money and buy one and not waste it on ideas that might not work and if it does work, it might not for long. Thats one of the BIGGEST expenses in this hobby, buying all the wrong equipment or a knock off that doesnt perform like the real thing and finally end up buying what you should have saved your money for in the first place.

 

I did see that kid doing it with maching wax, but I think that idea sounds good but dont know how well can it be constructed. I think people have used sprinkler valves for automatic water changes (im going to try and look up the threads)

Money is not the only problem, (I have bought things for my tank much more expensive that were not even that neccesary) Its about coming up with cheaper alternatives as well. Plus If i can control things more (if I buy a micro board that hooks up to pc I can create have a lot of customization. I know what you mean geek, but all it will cost me is basically 60 bucks for solenoids (And I have one alread so 45), all the other stuff I already have.