DIY Water changer - please review

[original kuhli]

I'm currently doing my plumbing for my new 75 gallon setup, it has (to this point) everything under the tank.

I'm not sure which way is the better way to go:

1 - seperate drain and fill
-a fill setup somewhat like this(www.aquahub.com/store/product26.html) and a pair of solenoids actuated by the float switch to stop filling
-a timed cycle to drain via my Aquacontroller Jr and a solenoid in a drain line

2 - Aquacontroller timed drain and fill
-same hardware as above but with the aquacontroller reading the float valve state and controlling the solenoids. This setup would allow the benefit of having discrete fill and drain times.

I'm probably going with these solenoids, can anyone speak for or against them? http://www.autotopoff.com/products/solenoid/index.htm.

This floatswitch looks to be the best as well. http://www.aquahub.com/store/madisonms8000.html

[original kuhli]

nobody? could use an opinion here...please.

[mistergreen]

why not just have a overfill/ water line drain?

A timed drain would need a pump or something right?

[PDX-PLT]

I think Scolley's system is based on the Aquacontroller; go read his "Kahuna" posts to see how he did it.

As for those solenoids, they have the advantage of being direct-acting; i.e., they don't require significant water pressure to function. On the other hand, they have a CV factor of only .28; i.e., with 1 PSI of pressure loss across them, the flow is only .28 GPM. Unfortunately, direct-acting valves with high CV factors are very expensive.

Liquid level switches can be obtained from many sources. Go to www.madisonco.com to find out more than you ever wanted to know about them.

[original kuhli]

I've been through Scolley's stuff many times. Indeed the larger diameter solenoids get expensive.

I'll run a line down through the wall so I'll just naturally siphon from the undertank plumbing system. The limited pressure within the system will help.

Thanks for the link to Madison.