View Full Version : Pump Flow Adjustment
GregAW
10-25-2008, 2:21 PM
Can someone tell me how to adjust down the flow of a submersable pump? I'm told that mine has too much flow but I didn't want to buy a new pump just now.
Thanks
Sploke
10-25-2008, 2:27 PM
You can use a ball valve on the outlet to restrict the flow.
GregAW
10-25-2008, 2:33 PM
Would the restricted flow damage the pump? Or would it just back wash out of the housing? I've got a Rio 3100 that puts out more flow than the 1" overflow pipe can feed.
Sploke
10-25-2008, 2:36 PM
No, it shouldn't damage the pump and it will actually run at a lower wattage because there will be less load on the pump. There is less water being pushed out of the volute by the impeller, so there is just less water drawn in.
GregAW
10-25-2008, 2:39 PM
Thanks Matt, Now, another question, how would you adjust the pump flow to coinside with the intake?
There are really only 2 ways to restrict flow coming out of the pump, the right way (putting a ball valve on the output) and the wrong way (putting a ball valve on the intake). If you restrict the intake side you will damage your pump, but if you restrict the output side, that is the same as adding more vertical lift to the pump and will not damage it even with the back pressure. You don't have to do anything on the intake side to slow it down or reduce it. I see your line of thinking, you want to slow down the impeller to get less flow, unfortunately, that isn't possible. That is where getting a lower rated pump comes in.
I have to ask though, what is "too much flow"? Can't you split the return line(s) to lessen the output coming out of the returns? Personally, I would work on keeping the flow as it is, just splitting it out to disperse the flow more instead of reducing the output of the pump.
GregAW
10-25-2008, 2:56 PM
Well, I've decided not to have this tank drilled. I was warned that without actually knowing what the glass is I run a big risk of it breaking so I went the the CPR CS90 overflow box. It is suppose to flow at 600 gph and the RIO 3100 flows (according to the advertisement) at 900 gph. What if I were to put a 3/4 to 1" fitting after the output pipe?
Well, you will have to try it out first and see. A 600GPH rated overflow can probably squeeze out close to 800GPH (You can always add a second U tube on the overflow box if your drain on the backside of the box is bigger than the diameter of the stock U tube, I did this method myself to increase my overflow box capacity). Also, a 900GPH pump after lift will probably only put out around 750GPH.. so it will be close, but it may just work out without making any changes. Unfortunately simply changing the diameter of the tubing coming off of the pump won't really reduce the flow that much. I will help some, but a ball valve would be much easier and cheaper to do. You can fine tune the flow with the valve, with just going different diameter tubing it is just a guess how it will work out until you try it.
GregAW
10-25-2008, 3:37 PM
Ace, You're right, a ball valve would allow for a better flow rate adjustment. Thanks. How's your tank coming along?
kcress
10-25-2008, 10:39 PM
Let me suggest a GATE valve instead of a ball valve. Gate valves are much better at adjusting flow than ball valves. Small changes with a ball valve can turn you into a drooling lunatic.
GregAW
10-25-2008, 10:55 PM
Let me suggest a GATE valve instead of a ball valve. Gate valves are much better at adjusting flow than ball valves. Small changes with a ball valve can turn you into a drooling lunatic.
I think I'm close!! :22_yikes: