Return pump flow rate question

[msbreton]

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]

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/pvc-pipes-equivalent-length-fittings-d_801.html


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

 

[MarkGP]

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]

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]

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

-Mike

 

[planedoc]

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]

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]

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

Thanks for the suggestions.

 

[planedoc]

Wow, thats a huge difference.

 

[ajcanale]

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

This is true.