Return pump and flow rate help

[Etto]

I've been putting my tank (4x2x2, 110gal) back together and finally got the water in last weekend. I have 2 returns, Main return with a Vectra M2 that goes straight to the tank, the second (COR20) is for the UV Sterilizer (Aqua 25 watt). The second return goes through a FS-100 flow sensor (1") then out the back of the tank into a closet I am using for controllers and water. My issue is that I don't understand what is going on with the flow. If I run the COR20 at 20% the flow sensor shows 173 GPH, if I crank it up to 100% it's still 173 GPH. I do have about 11-12 ft of head pressure.

Does this make sense? I know that the GPH would be decreased because of all the head pressure, but this doesn't make sense. The Sensor is new, but the pump is about 2 years old. Could it be that the pump is crapping out?

Thanks for any advice.

 

[MischiefReef]

I've been putting my tank (4x2x2, 110gal) back together and finally got the water in last weekend. I have 2 returns, Main return with a Vectra M2 that goes straight to the tank, the second (COR20) is for the UV Sterilizer (Aqua 25 watt). The second return goes through a FS-100 flow sensor (1") then out the back of the tank into a closet I am using for controllers and water. My issue is that I don't understand what is going on with the flow. If I run the COR20 at 20% the flow sensor shows 173 GPH, if I crank it up to 100% it's still 173 GPH. I do have about 11-12 ft of head pressure.

Does this make sense? I know that the GPH would be decreased because of all the head pressure, but this doesn't make sense. The Sensor is new, but the pump is about 2 years old. Could it be that the pump is crapping out?

Thanks for any advice.

Indeed, I would suspect head pressure is at play here. Aside from UV, What other equipment is attached to the cr20 side? Approx how much total pipe length on that run? How many bends in the pipe? I’m not a fluid mechanics expert by any means, but from past experiences with complicated systems with lots of twists in the hard pipe, you can get issues such as air locking which further limit flow. Not sure if that’s the case here, but hope my anecdotal experience helps in some way!

 

[Etto]

Indeed, I would suspect head pressure is at play here. Aside from UV, What other equipment is attached to the cr20 side? Approx how much total pipe length on that run? How many bends in the pipe? I’m not a fluid mechanics expert by any means, but from past experiences with complicated systems with lots of twists in the hard pipe, you can get issues such as air locking which further limit flow. Not sure if that’s the case here, but hope my anecdotal experience helps in some way

The pump thru the wall there is 1 90, 1 45, about 2 ft of horizontal and 1 ft vertical
Then a 90 into the UV (all pipe from pump to UV is 1"), exits the UV into 3/4" pipe, 2 ft horizontal out the UV to a 90 and a 90 back thru the wall
Behind the tank there are 5 90s to get back into the tank and about 2 ft horizontal. The reason for the 90s is to bring it thru the overflow.

Why would I have the same flow at 20% and 100%?

 

[MischiefReef]

As I noted, I’m no fluid mechanic expert, but my understanding would be that perhaps your pump is struggling to overcome some sort of air lock back pressure. Does the flow stay the same for a long time, or is there any indication it is fluctuating? Sometimes for complex systems it can take a while for the pump to get up to full flow rate, although the exact mechanics or causes of this I am not sure of.
Some other things I can think of is perhaps something obvious is being overlooked:
Are there any flow regulators/ball valves in that part of the system?
How is the pump flow controlled? Manual or remotely?
Are you certain your pump is communicating with the controller and actually ramping up to 100%?
Unfortunately I have no experience with your particular pump either. But if controlling remotely, is there any manual flow control on the pump itself?

 

[Etto]

As I noted, I’m no fluid mechanic expert, but my understanding would be that perhaps your pump is struggling to overcome some sort of air lock back pressure. Does the flow stay the same for a long time, or is there any indication it is fluctuating? Sometimes for complex systems it can take a while for the pump to get up to full flow rate, although the exact mechanics or causes of this I am not sure of.
Some other things I can think of is perhaps something obvious is being overlooked:
Are there any flow regulators/ball valves in that part of the system?
How is the pump flow controlled? Manual or remotely?
Are you certain your pump is communicating with the controller and actually ramping up to 100%?
Unfortunately I have no experience with your particular pump either. But if controlling remotely, is there any manual flow control on the pump itself?

I did take the pump apart and it looked like the O-ring was loose. I put it back together and was getting about 290 gph. I ordered a new O-ring just in case it's an issue.

Great advice though. I was changing the flow rate on the Apex Fusion and it was stating that the flow changed (50%). When I checked the pump controller it was only at about 20 gph, when I adjusted it on the controller to what should be 50%, I'm now getting about 450 gph. That will give me a change rate of about 4-5x per hour.

I think I'll put a ticket in with Neptune to see why I'm having the controller issue.

Thank for your help.

 

[MischiefReef]

I did take the pump apart and it looked like the O-ring was loose. I put it back together and was getting about 290 gph. I ordered a new O-ring just in case it's an issue.

Great advice though. I was changing the flow rate on the Apex Fusion and it was stating that the flow changed (50%). When I checked the pump controller it was only at about 20 gph, when I adjusted it on the controller to what should be 50%, I'm now getting about 450 gph. That will give me a change rate of about 4-5x per hour.

I think I'll put a ticket in with Neptune to see why I'm having the controller issue.

Thank for your help.

My pleasure. Sometimes an extra set of eyes on the problem is all that’s needed!