Return pump flow rate question

msbreton · 08/13/2012, 03:52 PM

I recently installed a UV sterilizer (this post isn't about discussing the effectiveness of such a purchase

) and thus become very interested in understanding my return flow rate. I have a Reef Tec 4000 and given my rise I should be getting ~800 gph (not accounting for other fittings).

I just tested my return flow (connect hose to return line and timed filling a 1g bucket) and was shocked to find I'm running less than 350 gph & maybe less than 300 gph. This is way too slow for the UV sterilizer so it's off for now.

How much of a reduction am I pay per 90? How about check valve and wide open ball valve? (I'd use the calculator but it doesn't include my pump). By the way, this is with the UV sterilizer hard plubmed. I have no idea how much flow it's reducing.

Any suggestions? Do I really need a larger pump? The flow should be more like 600 gph to have the UV kill rate at an acceptable level.

Thanks!

-Mike

planedoc · 08/13/2012, 05:07 PM

It's hard to run a true test as it takes a few minutes for flow in tank to stabilize and if you start draining into bucket you are changing water pressure going into pump.
Anyway this might help you
http://www.engineeringtoolbox.com/pv...ngs-d_801.html

Also I thought the slower the flow the better a uv will work.

MarkGP · 08/13/2012, 05:44 PM

What size return line are you using coming off the pump? That pump rating of 1000 gph at 0 head is most likely with a certain size pipe. If you have smaller than recommended it would result in a lower flow.

msbreton · 08/13/2012, 06:03 PM

The slower the flow the higher the kill rate but you shouldn't go below 400 GPH /w a 25w bulb as you'll then start killing off good bacteria, which is what's happening to me. Run the UV for a couple of days and I start to see ammonia and nitrites!

Using 3/4 for the return line.

msbreton · 08/14/2012, 11:24 AM

Is 3/4 the way to go for return plumbing or do people use 1"?

-Mike

planedoc · 08/14/2012, 03:30 PM

If you go to the web site I provided you above you would see that 3/4" pipe has over 50% more pressure loss per foot of pipe than 1". I run 1 1/2 from pump and than its reduced into two 1" pipes after the split. Just remember were only talking about 6 to 10 feet of pipe so fittings come into play more than pipe length and a 3/4" 90 is a lot worse than a 1" 90

msbreton · 08/14/2012, 04:46 PM

ah, very interesting, I missed that. hmmm the fittings on the UV sterilizer are 3/4. I wonder how much benefit I'd get changing the whole return line to 1" if I still have to go down to 3/4 to enter/exit the sterilizer.

Any thoughts?

P.S. Thanks again!

-Mike

msbreton · 09/15/2012, 02:18 PM

Update. Replumbed with 1" vs 3/4. Flow doubled! Went from ~345 to ~695. Much better!

Thanks for the suggestions.

planedoc · 09/15/2012, 02:34 PM

Wow, thats a huge difference.

ajcanale · 09/15/2012, 02:49 PM

Quote:

Originally Posted by planedoc

Also I thought the slower the flow the better a uv will work.

This is true.

08/13/2012, 03:52 PM	#1
msbreton Registered Member Join Date: Jul 2012 Posts: 138	Return pump flow rate question I recently installed a UV sterilizer (this post isn't about discussing the effectiveness of such a purchase ) and thus become very interested in understanding my return flow rate. I have a Reef Tec 4000 and given my rise I should be getting ~800 gph (not accounting for other fittings). I just tested my return flow (connect hose to return line and timed filling a 1g bucket) and was shocked to find I'm running less than 350 gph & maybe less than 300 gph. This is way too slow for the UV sterilizer so it's off for now. How much of a reduction am I pay per 90? How about check valve and wide open ball valve? (I'd use the calculator but it doesn't include my pump). By the way, this is with the UV sterilizer hard plubmed. I have no idea how much flow it's reducing. Any suggestions? Do I really need a larger pump? The flow should be more like 600 gph to have the UV kill rate at an acceptable level. Thanks! -Mike

09/15/2012, 02:18 PM	#8
msbreton Registered Member Join Date: Jul 2012 Posts: 138	Update. Replumbed with 1" vs 3/4. Flow doubled! Went from ~345 to ~695. Much better! Thanks for the suggestions. __________________ Tank Info:75gal mixed reef-134lbs LR & 40lbs sand, Eshopps PF-1000 overflow, RS-1000 sump (20gal), Fuge (10g), Reef Octopus eSsence S-130 Skimmer, Reef Tec 400 pump, Aqua 25w UV, VorTech MP40wES, 2 Ra

08/13/2012, 05:07 PM	#2
planedoc Registered Member Join Date: Jul 2012 Posts: 535	It's hard to run a true test as it takes a few minutes for flow in tank to stabilize and if you start draining into bucket you are changing water pressure going into pump. Anyway this might help you http://www.engineeringtoolbox.com/pv...ngs-d_801.html Also I thought the slower the flow the better a uv will work.

08/13/2012, 05:44 PM	#3
MarkGP Why do I do this? Join Date: Dec 2005 Location: Bristol, RI Posts: 1,015	What size return line are you using coming off the pump? That pump rating of 1000 gph at 0 head is most likely with a certain size pipe. If you have smaller than recommended it would result in a lower flow.

08/13/2012, 06:03 PM	#4
msbreton Registered Member Join Date: Jul 2012 Posts: 138	The slower the flow the higher the kill rate but you shouldn't go below 400 GPH /w a 25w bulb as you'll then start killing off good bacteria, which is what's happening to me. Run the UV for a couple of days and I start to see ammonia and nitrites! Using 3/4 for the return line.

08/14/2012, 11:24 AM	#5
msbreton Registered Member Join Date: Jul 2012 Posts: 138	Is 3/4 the way to go for return plumbing or do people use 1"? -Mike

08/14/2012, 03:30 PM	#6
planedoc Registered Member Join Date: Jul 2012 Posts: 535	If you go to the web site I provided you above you would see that 3/4" pipe has over 50% more pressure loss per foot of pipe than 1". I run 1 1/2 from pump and than its reduced into two 1" pipes after the split. Just remember were only talking about 6 to 10 feet of pipe so fittings come into play more than pipe length and a 3/4" 90 is a lot worse than a 1" 90

08/14/2012, 04:46 PM	#7
msbreton Registered Member Join Date: Jul 2012 Posts: 138	ah, very interesting, I missed that. hmmm the fittings on the UV sterilizer are 3/4. I wonder how much benefit I'd get changing the whole return line to 1" if I still have to go down to 3/4 to enter/exit the sterilizer. Any thoughts? P.S. Thanks again! -Mike

09/15/2012, 02:34 PM	#9
planedoc Registered Member Join Date: Jul 2012 Posts: 535	Wow, thats a huge difference.