Backyard Aquaponics
A place to discuss aquaponics

actually electronic speed control is IDEAL for pumps......VSD/vfd.

I wouldnt try to restrict the flow on the output of your pump as it creates back pressure that the pump may not handle....I would tee off the main line and put a tap in that line and vary the blled flow instead..and run it back into the tank...btw the john valves are called gate valves

Good points BK....that's what I did (tee off the main line and put a tap in that line)

Hey Dave. I have changed all my ball valves to gate valves with great results. They are much easier to adjust. I also have an extra pipe that flows back to the fish tank by-passing the GB's. By adjusting the by-pass I can also adjust the amount of water flowing into the GB's.

Thanks for the info everybody!

Joyce are the gate valves readily available like from a home improvement store that starts with the letter "Lowe's" ? Are they much more expensive?

PWM speed controllers are commonly used in HVAC air blowers. I tried one on Steve and anges pump with mixed results. Got a reasonable abounbt of flow control range, but that was with the motor running.

When you actually tried to start it from power off state often it would not start, which would lead to a catastrophic over heat. Thus the "effective" speed control range whle still allowing start-up was quite small. I know that our blower motors have / require very little starting torque, pumps are probably different.

For the record the blowers i'm talking about and the pump i tested were both "permanent spit phase" (start + run windings with a run capacitor in series with the start winding)

If you want to spend $800+ dollars you can get a proper VSD with speed and torque control over full range of rpm, but i think not

Actually BK i know for a fact that with centrifugal blowers they are under their MINIMUM load when the outlet is blocked. I'm sure i have read that its better to restrict on the outlet of a centrifugal pump than on the inlet as it may overheat otherwise, but i may also be full of shit

Will call our motor guy (also does pumps and blowers) tomrrow and get a ruling

I say allow bypass via pick up line after the pump!

we do this all the time in hospitals and universitys using high pressure cenrifugal multistage pumps on Reverse Osmosis Units and it dont seem to cause problems anywhere

as long as you dont dead head them most pumps can handle a bit of back pressure

Sure seems like the easiest solution to the problem with the added benifit of extra airattion in the fish tank

Cheers

To sumarise for you then...............

If you need the extra airation bypass flow back to the tank, if not then you should safely be able to restrict pump outlet.

would be interesting to measure current draw with both options.............

yep is all good but most of us are using "cheap" pumps lmao..pond pumps etc....any extra back pressure on them in time would burn the motor out.
Even my fish tank filter suggests to leave all valves fully open so the flow isnt restricted to maximise the pump motor life

Yeh some of us with cheaper pumps, allow water to bypass the impeller.
The problem with this is that the gap between the body of the pump and the impeller get ground away with impurities.
Which results in loss of flow, until it doesn't pump anymore!

I agree with the dead head on the THAT type of pump as the motor with a dead head is allowed to spin faster..I think it might be the same with adjustable guide vane pumps/blowers. Both under load will draw more current