Plumbing Question???

[vincejo28]

This might be kind of a dumb question…..but is there any reason why you should not put a ball valve on the intake of a pump instead of the out. It is a closed loop system and all the valve is for is to control the amount of water flow, not used as a shut off or anything. Reason why I ask is that it would be much easier plumbing and a lot less 90 degree turns! It will help in keeping the number of joints to a minimum and the number of 90degree turns low to keep good water pressure. Any help is greatly appreciated.
Thanks
Joe

[Timothy01]

first the water usally returns from the return side when power is cut( that has been my exp. could be wrong.) secondly you want to control the output which in turn will control your input so if you slow the flow from the input you may actully have water all over your flow because the the input wont keep up with the output. try using a few 45's insted of the 90's it wont decrease your flow nearly as much

[tabndust]

i like to put a valve and union on both sides or every pump, so i can shut both off and remove pump for cleaning and repair

[jdieck]

Actually Tabndust is right, if you have room put valves at the input and output so you can isolate the pump and remove it for maintenance without having to empty the pipes. Use ball union valves with the union to the pipe side of the pump.
Now having said that you can only use the valve in the pump ouput for flow control. The reason has to do with the design of the pump. Centrifugal pumps require net positive suction pressure in the inlet to function properly, if you restric the flow at the inlet the pump will try to pull instead of pushing creating negative pressure (vaccum) at the pump inlet, this vaccum generate bubbles (called cavitation) which increase noise and vibration with potential damage to seals and/or bearings. Also cavitation will reduce the pumps performance wasting power.
You do not have this effect if restricting the pump outlet.
By the way, for improved performance try selecting a pump that closely matches your flow requirments and if possible increase the diameter of the inlet. Do not guide yourself by the size of the pump connection at the inlet. Most Iwakis have 1" inlet but require 11/2" or 2" in the inlet. Mag drives 9 and higher have inlets of 3/4" but the manufacturer recomends 11/2" for the inlet and discharge pipes. etc.

[vincejo28]

Thats what i needed to know!!
Thanks everyone!