SCWD Help

[ismvel]

Just purchased a SCWD from someone but it isn't alternating the flow. It is coming out of both ends simultaneously. Anyone tell me why this is happening?

The inside mechanism is spinning freely, so the initial gear isn't stuck. I am hoping it is an easy fix and I don't have to mail it back to her.
Thanks.....

[caferacermike]

Is it installed on a large enough pump?

[captexas]

What size pump do you have it on? It could be one of two things, either the pump isn't pushing enough water through it to get the mechanism to work properly or the mechanism itself is broken. I've had one or two go bad on me. After they have been used and then sit dry for awhile, the little plastic parts inside can become very brittle. Then when you put it on a pump the water pressure breaks it.

[ismvel]

Well it is supposed to work on pumps from 50 - 1400 gph....I bought a Rio 2100 yesterday that pushes 692 I beleive.....so it isn't an extremely strong pump, but still strong enough to push it.....

[glennr1978]

sounds like it may be defective.

[ismvel]

That is what I am leaning towards.....we'll see...someone on a different site posted this...

SCWD's are notorious for getting jammed with calcium deposits or small pieces of sand. Try soaking it in white vinegar for a couple hours to break up any particle. If that doesn't do it, then it is probably a broken gear.

The way it works is:

Water enters throught the bottom and spins a small turbine gear. The turbine gear is connected to a shaft that spins another small gear. That small gear spins a larger gear that is connected to a rotating gate. As the gate rotates, it covers one outlet and leaves the other outlet uncovered. There is a point in the rotation where both outlets will be partially open and this is the position where the SCWD normally clogs.

I had some pictures of one cut in half, but now I can't find them. I'll keep looking and post them if I find them.

I modified mine by cutting off the three connections and glueing on 3/4" threaded fittings with #16 weld-on. This effectively doubled the inlet and outlet size for better water flow. It is a very delicate operation because the plastic case is not very thick and it doesn't leave much room for error. I have it hooked up to a Mag 18 returning from my sump. I figure I am pushing about 1200gph and it switches outlets every 15 seconds or so.

Compared to the original design data, that's a significant increase. And since I did the modification (9 months ago) it hasn't clogged once.

[captexas]

Yeah, like most equipment in this hobby, they do require some routine cleaning. If you haven't already, try soaking it in vinegar for awhile. Then rinse it really well and give it another try. If it still doesn't work, it probably is a broken piece inside. I had two on a 75g a few years ago and then replaced them with Sea Swirls. I let the SCWDs sit dry for many months and then when I tried using them on another tank, I found one had dried up and broke inside. I never did take it completely apart to look inside, but the pieces that I could see look like they were pretty thin plastic.