Are ball valves ok to use on return lines?

[Kevin Guthrie]

I have a killawatt meter and I noted an uptick in wattage when I switched my Iwaki from upstairs (high head) to downstairs (3 foot head) some years back.

It may seem counter-intuitive - you might think the impeller has to push against increased resistance when the outlet is throttled down. But actually the opposite happens. Here is why.

Consider a pump with a wide open outlet. Water is coming at basically a standstill. The impeller has to work hard to accelerate the water from dead stop up to speed and kick it out of the chamber. There is a lot of resistance to the impeller spinning.

Consider a pump with a completely closed outlet. Once the pump has been running for a second or two the water in the chamber is spinning at almost the same speed as the impeller. The impeller doesn't have to accelerate water as much, resistance to the impeller is very small.

A pump with an outlet throttled half way will be somewhere in between.

Or... a pump throttled down is doing less work, hence it uses less power.

 

[kenandmoose2]

Good explanation Kevin

This has gotten out of control in here. Y'all that don't work with pumps on a regular basis don't really understand amp draw......The pump over sized is not an issue. Put a "minimum flow" or as some of you are calling it a recirculating loop.... whatever.... Build a manifold off of the discharge and use it for a carbon or bio pellet reactor or something.

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[Green Chromis]

:fish1: I use True Union ball valves on both the intake and exhaust of all my pumps. They are all external Iwaki pressure rated pumps, with the Japanese motors, and I need the ball valves on both sides, so I can shut off the water flow from both sides when doing maintenance on the pumps or changing out the pumps. I always keep one or two of the same size pumps as spare in case of pump failure, and the ball valves make it a breeze to change them out, and by the way, I don't give a darn if I use a little extra power because of this, and neither should anyone else. :fish1:

 

[heathlindner25]

:fish1: I use True Union ball valves on both the intake and exhaust of all my pumps. They are all external Iwaki pressure rated pumps, with the Japanese motors, and I need the ball valves on both sides, so I can shut off the water flow from both sides when doing maintenance on the pumps or changing out the pumps. I always keep one or two of the same size pumps as spare in case of pump failure, and the ball valves make it a breeze to change them out, and by the way, I don't give a darn if I use a little extra power because of this, and neither should anyone else. :fish1:

For an external pump application, this is the only way to do it.

 

[Green Chromis]

For an external pump application, this is the only way to do it.

:fish1: You are 100% correct, never did like internal pumps, due to pump failure in tank or sump, plus the additional heat added to the water. :fish1:

 

[dcmartinpc]

I think it is an important distinction to note that while it is perfectly fine and recommended for maintenance in most cases to have a true union ball valve on the inlet, it is never ok to restrict the flow on the inlet with a valve.

Don


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[heathlindner25]

Definitely ,the inlet valves are for maintenance purposes.