Pentair UV Killing Flow

[JPK_Esquire]

I recently bought a Pentair Smart UV 40 watt sterilizer for my 180g tank. I recognize this is a bit overkill, but the Smart UV 25 watt says it is only rated up to 130g. So my 180g is in between. I bought the UV Sterilizer as a preventive against algae and bacteria (fish are being purchase quarantined so not as much of a need to combat protozoans etc.). Initially I plumbed attached to the roof of the inside of the stand, running off my Neptune COR-20 return pump (I've got two dual return pumps -- COR-20 and COR-15 using 3/4" tubing). The flow sensor showed there was only about 520 gph flowing off of the COR-20, which is not even close to the 943-1575 gph recommended by the manufacturer to combat algae and bacteria. So I took it down and off the return pump, and bought a separate pump solely to run the UV (Sicce Syncra Silent 5 -- 1321gph). Once hooked up to the UV and with little head pressure (just over the side of the sump), I am still only getting 550-600 gph (confirmed with Neptune Flow Sensor and bucket test). When I just test the flow rate of the pump, its 1200-1250 gph. So the Pentair is really slowing it down. I recognize that the sterilizer is 4 feet long, but I've got it running horizontally.

Anyone else have these same problems of the Pentair UV slowing the flow down THAT much? 800 gph? Really?

I am wondering whether the issue is that I am using 3/4" tubing. The UV comes with 1 1/4" unions. So maybe find a pump with a 1"outlet and use 1" tubing?

Any assistance would be greatly greatly appreciated. Alternatively, if anyone thinks the Pentair Smart UV 25 Watt would be fine, that model only requires 472-722 gph, which I could do with the Sicce.

Thanks in advance.

 

[CuzzA]

I recently bought a Pentair Smart UV 40 watt sterilizer for my 180g tank. I recognize this is a bit overkill, but the Smart UV 25 watt says it is only rated up to 130g. So my 180g is in between. I bought the UV Sterilizer as a preventive against algae and bacteria (fish are being purchase quarantined so not as much of a need to combat protozoans etc.). Initially I plumbed attached to the roof of the inside of the stand, running off my Neptune COR-20 return pump (I've got two dual return pumps -- COR-20 and COR-15 using 3/4" tubing). The flow sensor showed there was only about 520 gph flowing off of the COR-20, which is not even close to the 943-1575 gph recommended by the manufacturer to combat algae and bacteria. So I took it down and off the return pump, and bought a separate pump solely to run the UV (Sicce Syncra Silent 5 -- 1321gph). Once hooked up to the UV and with little head pressure (just over the side of the sump), I am still only getting 550-600 gph (confirmed with Neptune Flow Sensor and bucket test). When I just test the flow rate of the pump, its 1200-1250 gph. So the Pentair is really slowing it down. I recognize that the sterilizer is 4 feet long, but I've got it running horizontally.

Anyone else have these same problems of the Pentair UV slowing the flow down THAT much? 800 gph? Really?

I am wondering whether the issue is that I am using 3/4" tubing. The UV comes with 1 1/4" unions. So maybe find a pump with a 1"outlet and use 1" tubing?

Any assistance would be greatly greatly appreciated. Alternatively, if anyone thinks the Pentair Smart UV 25 Watt would be fine, that model only requires 472-722 gph, which I could do with the Sicce.

Thanks in advance.

How is it oriented? You mention attached to the ceiling of the stand which suggests to me that it is horizontal with outlets down or to the side. This is an incorrect way to install a UV. Read the manual and it will show the correct orientation. Either horizontal with inlet and outlet facing up, slightly angled up toward the outlet OR vertical feeding top to bottom. Flow should be controlled on the inlet, not the outlet. If my suspicions are correct and you have it oriented wrong, it is likely trapping air reducing the flow.

 

[JPK_Esquire]

How is it oriented? You mention attached to the ceiling of the stand which suggests to me that it is horizontal with outlets down or to the side. This is an incorrect way to install a UV. Read the manual and it will show the correct orientation. Either horizontal with inlet and outlet facing up, slightly angled up toward the outlet OR vertical feeding top to bottom. Flow should be controlled on the inlet, not the outlet. If my suspicions are correct and you have it oriented wrong, it is likely trapping air reducing the flow.

Yeah that was my original thought as well. When attached to the ceiling, the inlet/outlets were down. However, when I disconnected from the return pump and attached to the dedicated pump, it was sitting on the ground horizontally with inlet/outlets pointing up. Still restriction.

 

[CuzzA]

Well, do a bucket test to calculate the flow rate. That is going to be far more reliable than a flow meter. You could bucket test the pump as well. Process of elimination.

 

[JPK_Esquire]

Well, do a bucket test to calculate the flow rate. That is going to be far more reliable than a flow meter. You could bucket test the pump as well. Process of elimination.

Yep! Great minds think alike. That's exactly what I did. I bucket tested attached to the UV, and the flow was pretty close to what the flow meter was saying (570 flow meter, approx. 600 with the bucket). Take the hose off the UV and the flow was about 1200 or so. Which, now that I think about it, means that the 3/4" hose likely isn't the issue because the pump was flowing 1200 gph. Put it in a 4 foot UV sterilizer and flow as cut in half. Pretty Amazing!

I started this thread so that people buying that UV know that they are going to have to get a pump flowing something 2500 gph or more to get the minimum 967 gph suggested by the manufacturer for algae and bacteria.

 

[ca1ore]

How are you attaching the tubing to the UV? If you are using 3/4”barb fittings, those may be the flow loss culprit. Take the hose off the UV, but keep the barb attached to the hose and measure flow. I’m not familiar with the internals of the pentair, but most UV housings are no worse than runs of PVC to flow.

 

[JPK_Esquire]

How are you attaching the tubing to the UV? If you are using 3/4”barb fittings, those may be the flow loss culprit. Take the hose off the UV, but keep the barb attached to the hose and measure flow. I’m not familiar with the internals of the pentair, but most UV housings are no worse than runs of PVC to flow.

Hmmm...Very Interesting. I will definitely try this, and will update with the results.

 

[CuzzA]

How is it oriented? You mention attached to the ceiling of the stand which suggests to me that it is horizontal with outlets down or to the side. This is an incorrect way to install a UV. Read the manual and it will show the correct orientation. Either horizontal with inlet and outlet facing up, slightly angled up toward the outlet OR vertical feeding top to bottom. Flow should be controlled on the inlet, not the outlet. If my suspicions are correct and you have it oriented wrong, it is likely trapping air reducing the flow.

Too late to edit, but for posterity I accidentally wrote in the vertical position feeding top to bottom. That is incorrect. The feed should go from bottom to top in order to purge air.

 

[JPK_Esquire]

Too late to edit, but for posterity I accidentally wrote in the vertical position feeding top to bottom. That is incorrect. The feed should go from bottom to top in order to purge air.

No problems. Couldn't run it horizontally as the wife wants it inside the cabinet and the cabinet is not tall enough to go vertically.

I am going to bucket test the flow with the barb still on tonight and see what it is. If it is slowing down with the barb, that is likely the culprit. If that IS the culprit, I may try to hard plumb it to the UV. Problem is I have to buy two new unions for the Pentair (which isn't cheap -- $33 for each), just to see if hard plumbing with two 90s going in and two 90s coming out, cuts the flow an equal amount to the barbs. $66 experiment?

 

[CuzzA]

No problems. Couldn't run it horizontally as the wife wants it inside the cabinet and the cabinet is not tall enough to go vertically.

I am going to bucket test the flow with the barb still on tonight and see what it is. If it is slowing down with the barb, that is likely the culprit. If that IS the culprit, I may try to hard plumb it to the UV. Problem is I have to buy two new unions for the Pentair (which isn't cheap -- $33 for each), just to see if hard plumbing with two 90s going in and two 90s coming out, cuts the flow an equal amount to the barbs. $66 experiment?

Their customer service is very helpful. I'd give them a call. The unions may be standard. I'd find out before I spent $66.

 

[Dj City]

I would bet the issue is the barb fittings.
That is a lot of reduction.

I'm glad I ran across this post as I have the same UV that will be going on my 180 build.

 

[JPK_Esquire]

I didn’t get to bucket test tonight (busy at work). However, I did watch the most recent BRS video on UV Sterilizers (9 min video in the 5 minute setup series) and Ryan mentioned you need to run 3x tank turnover through the UV if the goal is combat/prevent algae and bacteria (much lower for protozoan and fish health). He also explains the reason for this (algae/bacteria multiple faster so you want it going through the UV more often, versus ich And other fish nasties take much longer to multiple so you want longer exposure in the UV to kill them). Pentair’s suggested 967 gph is based upon a rating of that UV for an aquarium up to 260 gallons. I did the math and that’s 3.67x turnover on a 260 gallon tank (pretty close to what Ryan suggested). Because my tank is only 180g (prob. 150-160 when you consider the rock and sand), that means I may only need something like 587 gph (160g*3.67 suggested turnover rate). Which happens to pretty dang close to what the Sicce was putting out.

I still plan to bucket test the bar fittings, but thought this info may be helpful for any others trying to size and set the flow on their UV.

 

[Dj City]

Any updates?

I installed mine today and the flow was even worse than yours. I was getting 120 - 130. This is with the UV being the only thing running off the manifold and the pump and gate valve both being wide open.
I'm using a Jebao DCT 10000 pump which pushes up to 2640gph with a head of 19ft.
I have 1/2 inch barb fittings on the UV in and out. I have 1/2 inch barb from the manifold.
I have 1/2 inch Apex flow sensor.
UV is mounted vertically. Intake on the bottom, output on top.

Any ideas?

 

[JPK_Esquire]

Any updates?

I installed mine today and the flow was even worse than yours. I was getting 120 - 130. This is with the UV being the only thing running off the manifold and the pump and gate valve both being wide open.
I'm using a Jebao DCT 10000 pump which pushes up to 2640gph with a head of 19ft.
I have 1/2 inch barb fittings on the UV in and out. I have 1/2 inch barb from the manifold.
I have 1/2 inch Apex flow sensor.
UV is mounted vertically. Intake on the bottom, output on top.

Any ideas?

Still haven't had a chance to test the flow with just the hose and barb attached. May have to wait until the weekend. Work has been nuts.

BTW: 1/2 inch flow sensor is probably causing problems for sure. I made this same mistake and bought the 1/2 inch flow sensor. However, if you read the fine print on the sensor you'll see it is only rated for up to 250 gph.

 

[Dj City]

Still haven't had a chance to test the flow with just the hose and barb attached. May have to wait until the weekend. Work has been nuts.

BTW: 1/2 inch flow sensor is probably causing problems for sure. I made this same mistake and bought the 1/2 inch flow sensor. However, if you read the fine print on the sensor you'll see it is only rated for up to 250 gph.

Oh wow.

I did not read the fine print. Two of the 1/2 inch sensors came with the 1 inch in the box.
I think im going to have to go up to 1 inch hard plumbing.
Sucks cause I will have to re-do my manifold.

 

[Dj City]

So the 1/2 inch sensor is only good for bio pellet reactor, gfo and other very slow flow devices.
Bummer!

 

[JPK_Esquire]

So the 1/2 inch sensor is only good for bio pellet reactor, gfo and other very slow flow devices.
Bummer!

Pretty much. I haven't sent mine back yet, but yeah...bummer.

 

[jschultzbass]

my return pump is rated for 2900 gph, it goes through 1.5" pipe, through my 2" flow meter, through my 57 watt UV and to my tank. Flow is only 950 gph. It's just the way the pumps work. If you look at the pump curve it doesn't take many feet of head pressure for the pump flow to plummet.

 

[jschultzbass]

according to the pump curve you have about 12 to 13 feet of head. Add the vertical height, horizontal length, any elbows, unions, stuff like that and you can easily have that much.

 

[JPK_Esquire]

according to the pump curve you have about 12 to 13 feet of head. Add the vertical height, horizontal length, any elbows, unions, stuff like that and you can easily have that much.

I had probably less than 18 inches of head height (just up and over the top of the sump) and then directly down into the UV, run the length of the UV (4 feet or so) then up the same 18 inches and back into the sump. I was using tubing so no elbows etc. That short 18 inches on both sides (so total 36 inches of head height) lost me 1,000 gph? I think it is the barbed fittings, just haven't had a chance to confirm yet. As I described above, when I just pump using the 3/4" hose, I got 1,200 gph with the exact same front-end head pressure.