UV flow issues

[MTShell]

Hello reefers,
I have recently finished cycling my 220 gallon and added a few CUC. I have a 57W Aqua UV classic plumbed into a manifold. That manifold is connected to the main return pipe. I have just measured the flow rate through the UV branch and I am only getting 400gph. Pump is sicce sdc9 running at 70% (to reduce noise a bit). In total I have 3 loc-line return nozzles, and 1 of them is from the UV.

I do not know what is the easiest way to increase the flow through my UV. I have no ball valves on my main return and downstream of the manifold branch, only upstream. So I cannot slow the main return flow to increase UV branch.

Should I buy a second pump and run that only on the UV? (worried about increase in noise)
Should I swap the 57 watt bulb to a 25 watt one? Heard that they are physically compatible, but have to do something with the ballast, which sounds complex.
Can I simply run the UV 6-8 hours a day? The dwell time is still long and I am worried that it will cook my plankton and copepods because it will still go through 10-14 tank volumes in 8 hours.
Even if I go ahead and cut out some of my return plumbing, install valves, close off almost fully my main return, just this pump will barely get to the required flow.

Thanks for any advice.

 

[Tangdora]

Do you have any pictures of your sump and manifold setup

 

[MTShell]

Do you have any pictures of your sump and manifold setup

Sure, will post it when i get home

 

[mmorrison55]

How are you measuring your gph? I think you will be ok with 400gph, just run it a bit longer, but if you want to increase the gph, you likely need to re do some plumbing.

I didn’t see you mention what size plumbing yiu have going from your return pump and into the UV and how many bends do yiu have before you reach the uv. If using 90 bends, and 3/4” plumbing, that will reduce the throughput quite a bit.

 

[mmorrison55]

You could also step down to the 25 watt model. It’s recommended 400-1200 gph.

Do you just run the one return pump?

I sold my 57 watt and bought two 25 watt units and plumbed them into my two return pumps so that all water going into the display is running through the uv

When I was running the 57 watt model, the gph measured by my apex flow meter was about the same range you are quoting and it seemed to get the job done.