Backyard Aquaponics
A place to discuss aquaponics

What do you base this on Charlie?...

I sell a lot of pumps and I get very few returned, in fact I haven't had one returned for a about 3-4 years now (touches wood). Of those returned the majority were due to two issues... (1). Pumps being run dry, and (2). Customers restricting the flow with a tap in the feed line, as the O.P. described, rather than bleeding off the extra flow/pressure through a 'T' piece with a valve etc.

Some of the pumps returned due to restricted flow had only lasted a month or two, but since I started educating my customers on how to circumvent this issue with a pressure by-pass, spray bar set-up etc, I've had no returns.

It does depend on the impeller design. The 3 common are the "propeller" (used in wave makers and not intended to lift), the "open impeller" (most pond pumps due to versatility) and the "closed impeller" (used in brands like Rio HF intended for high head pressures).

Restricting the output of a mag-drive open impeller pond pump is no different to increasing the head height. Really only its inefficiency to lift is reduced although it may reduce electrical life in pumps with light windings and magnets.

It is easy enough to let the line run all the way around the system with the excess going back in the FT or ST, right? I've got a final ball valve at the end of the line to create the back pressure needed to make setting the GB inflows to the levels I need

Yes boss, that is another way of doing it.

may cost a little more in piping, may give a little easier flow control.

What setup is better over all , constant flood, or flood and drain?

BYAP tests show they are both the same.
some people try to swear that F&D is better.
constant flood means you can have a smaller sump.

The flood and drain ensures that water goes to every corner of the bed, so the bacteria has a chance to work at it's max, and the plants get the freshest (or dirties, however you want to look at it) water.

I've got both in my system, and my F&D bed out performs my constant flood.

However, somebody else could do the exact same thing, and discover that their constant flood does better.

For last few months, because of dodgy bell syphon design (my fault not the bell syphon principle), I've been running my smaller system on flood and drain for a bit over two weeks then constant flood for a bit under a fortnight (while away at FIFO work). The plants don't seem to mind either way.

I've fixed the bell syphon now (thanks to Mr Damage) and will run it flood and drain all the time... not so much because I think it's better than constant flood but because I love its physics and simplicity. I didn't believe it would work when I first read about it and even after nearly two years, I get a tiny little kick each time it makes and breaks... and it sounds so good too