I made a glass bell siphon in an attempt to discover what actually goes on in one as it starts to siphon. It involved taking a glass jar, and turning it upside down.
I think the key when building a siphon is to place a tap at some point on the hose coming from the pump to allow a small percent of the flow to be diverted. This allows you to increase or decrease the flow and makes making a siphon very easy. The most difficult thing to get right is to match the flow against the size of the standpipe (the standpipe is the white PVC pipe the water drains out of the bucket through.
in this video...
- the siphon starts at around 00:20. Even though there is some flow before 20 seconds in, it doesn't really start properly until enough water is entering the standpipe to create the required suction)
- then stops at around 00:40. Note the rush of air in through the small hose within the jar and how quickly it stops the siphon.
- then the cycle repeats.
A bell siphon does that. It also generates a tide-like ebb and flow in the grow bed(s). This test siphon is in a small bucket, so the time it takes to flood and drain is only a few seconds. We could flood and drain as fast as this in aquaponics, but would then normally turn the pump off for up to an hour each cycle in order to let the plants breath for a bit. Alternatively we might use a smaller pump and run it all the time.
Okay, FINALLY I get the whole bell siphon thing! I couldn't figure out how the bubble in the top would get eliminated, to create the siphon. I wasn't picturing it getting sucked into the standpipe by the water flow. NOW it all makes sense. (I'm slowly working my way through your blog, to leech all the knowledge I can from your aquaponics trials and failures and successes. I'm trying VERY hard not to get distracted by other things, like solar panels. One thing at a time...or two. Maybe two would be okay...)
ReplyDeleteDramatic isn't it.
ReplyDeleteI miss my siphons :)
-Bullwinkle