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Ways of bleeding off pump flow?
http://byap.backyardmagazines.com/forum/viewtopic.php?f=8&t=1871		 Page 1 of 2
Author:  Dave Donley [ Jul 31st, '07, 01:59 ]
Post subject:  Ways of bleeding off pump flow?
I need to reduce the flow to my beds so the siphons can quit easily. There is a 3/4" pipe going from the pump, vertically up about four feet, then over about six feet to the beds. I was thinking about placing a tee in the vertical pipe, and putting a ball valve after the tee then an elbow back down into the sump to return some of the flow to the sump instead of going to the beds.

Would it be better to put the tee lower or higher on the vertical pipe? I am thinking higher would give finer control, as there would be less pressure up there.

Are there any better ways of doing this sort of thing? (I tried putting 1" long sections of garden hose down in the pipe but that hasn't slowed it down enough)
Author:  janethesselberth [ Jul 31st, '07, 02:26 ]
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My ball valves stick when you turn them, such that I don't think the pressure is going to make that much difference in tuning the flow. My difficulties in adjusting the flows with ball valves come more from trying to turn them juuuuuuust a little, then having them break loose, and turn too much! I would vote for putting the ball valve where it is most convenient. (I have 4 ball valves - one to adjust the flow that circulates back to the tank and 3 to adjust each bed. That first one is like the coarse adjustment, and the other 3 are fine tuning.)
Author:  mokevinb [ Jul 31st, '07, 03:12 ]
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One way my father told me, many years ago, to reduce pressure was to increase the diameter of the supply line. I don't know how well this will work when you are trying to use smaller diameter terminal lines. Of course, one option is install a valve at the end of your supply run and add a return line to your supply source. If necessary go up to an inch and half, this will reduce your water pressure by half or more.

Kevin
Author:  meancoyote [ Jul 31st, '07, 04:41 ]
Post subject: 
what about reducing the power to the pump?
Author:  janethesselberth [ Jul 31st, '07, 05:46 ]
Post subject: 
If you have the capacity, it makes sense to keep the water moving rather than reducing power to a pump. Also, I'd worry about whether the pump is designed to operate at reduced power. (Admittedly, I know -nothing- about the operation of electrical devices.)
Author:  Food&Fish [ Jul 31st, '07, 05:52 ]
Post subject:  Re: Ways of bleeding off pump flow?
Hi dd there are 2 ways of looking at it pressure and volume .Say your pump is rated at 400 litres per hr run that threw a 2 in pipe you will get no pressure then run it threw a 1/2 in pipe there will be a lot more pressure but you will still have roughly the same volume [still to much water ] so the best is bleed it off .Does not realy matter where as jannet said where its conveniant .Me i run a large water line then smaller offf to the grow beds [In 12 months have had virtuly on adjustments]
Author:  Hex [ Jul 31st, '07, 06:31 ]
Post subject: 
I guess you could put two valves in. One after the pump outlet but before the tee which serves to adjust the main flow and could double as an isolator. Put the second valve on the outlet side of the tee to control the flow back to the tank. The open side of the tee goes to the growbed. Between the two valves you should have a lot of control.
Author:  TimC [ Jul 31st, '07, 08:55 ]
Post subject: 
Water will take the shortest and easiest path HEX. You would find if you opened the ball valve completely then it will isolate the other pipe as it can't build enough pressure.

As the for the valves sticking, I just used a bit of lube (vasaline I think) and it worked a treat. The more you actuate them the easier they become to adjust.

I do the exact same thing DD, tee and a tap. Plenty of oxygenation and gives good control over the water flows.
Author:  Jim Atkinson [ Jul 31st, '07, 10:56 ]
Post subject: 
The real answer is to replace the ball valves with what used to be called John valves- like a tap with a big round handle and a slide which moves in the housing.- just turn to restrict the water flow- Joel mentions in his book that ball valves are just way too hard to make small adjustments with.
It is no problem for a pump to be restricted in this way.
Author:  meancoyote [ Jul 31st, '07, 10:59 ]
Post subject: 
it seems a waste of energy though.
Author:  Jim Atkinson [ Jul 31st, '07, 11:28 ]
Post subject: 
The other possibilties would have to be a smaller pump or a DC pump. DC pumps are hard to find in useful sizes and require a completely different power supply but they will run quite happily at reduced voltages.
I wonder if anyone on this forum knows if you can use a dimmer type circuit on an AC pump?
Author:  meancoyote [ Jul 31st, '07, 11:29 ]
Post subject: 
i use a dimmer switch on my forge blower, it is a ac motor. maybe a pump is differnt?
Author:  Hex [ Jul 31st, '07, 13:54 ]
Post subject: 
It will depend a lot on the motor type. You`d need a dimmer rated for inductive loads, most can only handle resistive.
Author:  TimC [ Jul 31st, '07, 15:18 ]
Post subject: 
Exactly Hex, most resistive dimmer switches just create heat and you end up using the same power. Reostats are very similar.

The better ways to do it are pulse width modulated or switch mode. But I say if you've got excess energy use it to oxygenate the water or run some DWC or NFT channels.
Author:  Hex [ Jul 31st, '07, 16:04 ]
Post subject: 
I think electronic speed control is more useful for fans than pumps.
If anyone is tempted to use a light dimmer as a speed controller be aware that it may generate large spikes which could total the insulation of your motor windings rendering it.. a door stop :wink:
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