Also called indexing valves
Hi Justin. When I was referring to "sequencers" I was actually referring to sequencing timers like the ones made by Rob Torcellini at Bigelow Brook Farm - http://www.theaquaponicstore.com/Sequencing-Timers-s/107.htm. These let you run a timed flood and drain cycle using two, or more, pumps so you can flood one or more beds, let it drain, then flood the next bed or beds...and avoid the risk of creating too low of a water level in your fish tank. Alan and I experimented with Indexing Valves for a while and found that they take a tremendous amount of water pressure (re: a much more powerful pump than you would typically need for the system otherwise) to work properly. Subsequently, I'm not a fan.
It really depends on your budget. The sequencing timers rock though. They're easy to use too. Plus I got to meet Rob. This guy has got his product DIALED in. Wow!!!
I'm really glad I came upon this post. Right now I currently have two pumps in my FT that fill/drain both of my GBs. Unfortunately both pumps are currently plugged into two separate analog recycle timers. Both timers are set to 8 minutes on/15 minutes off. However, with anything analog the timing sequence is at the mercy of a turning knob. Also, I've found that these knobs can be often bumped into screwing up you flood/drain cycles completely. I researched indexing valves but the smallest I can seem to find fits 1" PVC. My system uses all 3/4" PVC. The fact that the sequencing timers Sylvia mentions can power two pumps at the same time and are digital is amazing! I'm so excited. Time to order.
I am a fan of my indexing valve in that I'm able to use one 50W, 400 gal per hour or so pump to flood six 100 gallon beds, in sequence, with no siphons and no sump. It works very well in my situation, going non stop for about a year now with fish in for 10 months or so.
I'm searching for a low wattage DC pump to drive my system and would like to use the DC sequencing timer in conjunction with my same indexing valve. We'll see how that works out in time.
Please provide detail as they arise George! I'd love to run something solar, DC in case I lose power!