Return lines & flow rate

[islandguy11]

I'm trying to better dial in flow rates for UV sterilizers on a couple of tanks, and have been wondering: does having a return line nozzle submerged (say just below the water surface) affect the flow rate compared to having the nozzle right above the water surface?

Seems like it should from a physics point of view, but I'm not sure if it's enough to translate into a significantly reduced flow rate measurement (as I can only check this when a nozzle is not submerged).

Thx for any input.

 

[esoxlucius]

Surely your pump is still pumping at the same rate whether your return nozzle is slightly above the surface or slightly submerged, therefore flow rate would be the same wouldn't it?

 

[markstrimaran]

Technically submerged will have slightly higher discharge pressure, thus less flow. But you would need very expensive guages to calculate the tiny difference.

 

[islandguy11]

Surely your pump is still pumping at the same rate whether your return nozzle is slightly above the surface or slightly submerged, therefore flow rate would be the same wouldn't it?

Thx for reply. Not exactly, as the head pressure will be a bit different, but I just didn't know how significant it would be -- appreciate your input markstrimaran .

I guess theoretically the deeper in your tank the return nozzle was, the more head pressure it would be dealing with, and thus slower flow rate coming out, but perhaps as Mark alludes to even that wouldn't be very measurable in most tanks.

I know a lot of peeps like the return line in the tank because it's noisy if above the water line -- I have my return line going into a small plastic container with a couple of decent sized holes drilled into the bottom, and with polyfil for a final polish of the water before it goes back into the tank; it makes very little if any noise (and it's much easier to check/monitor UV sterilizer flow rate).

 

[esoxlucius]

Thx for reply. Not exactly, as the head pressure will be a bit different, but I just didn't know how significant it would be -- appreciate your input markstrimaran .

I guess theoretically the deeper in your tank the return nozzle was, the more head pressure it would be dealing with, and thus slower flow rate coming out, but perhaps as Mark alludes to even that wouldn't be very measurable in most tanks.

I know a lot of peeps like the return line in the tank because it's noisy if above the water line -- I have my return line going into a small plastic container with a couple of decent sized holes drilled into the bottom, and with polyfil for a final polish of the water before it goes back into the tank; it makes very little if any noise (and it's much easier to check/monitor UV sterilizer flow rate).

View attachment 1342744

Ahh, I understand now, never was much good at physics! Nice tank by the way, i'm being drawn to minimalistic tanks more and more these days. I hope those aren't a pair of ming vases in your tank!

 

[islandguy11]

Ha ha, I wish they were Esoxlucius -- then I'd sell them, buy a couple of 1000 gallon aquariums plus a beach side villa to house these.

While I do appreciate and like seeing others' natural style tanks, personally I appreciate the ease and cleanliness of a more minimalist set up, esp. when it comes to a solitary showpiece fish (but likewise think a totally bare bottom set up is not very attractive).

 

[duanes]

To optimize a UV system, the slower the flow rate, means the longer contact and kill time under the UV.
If flow is to quick, the UV achieves nothing.
To me taking a Tee off the main line for a separate flow line tthru the UV unit, using a valve of some sort, to control flow to maintain long contact time is always the best method, allowing the other main lines flow to remain normal, with enough to aerate, and promote current in the tank.

 

[islandguy11]

To optimize a UV system, the slower the flow rate, means the longer contact and kill time under the UV.
If flow is to quick, the UV achieves nothing.
To me taking a Tee off the main line for a separate flow line thru the UV unit, using a valve of some sort, to control flow to maintain long contact time is always the best method, allowing the other main lines flow to remain normal, with enough to aerate, and promote current in the tank.

Thanks for input Duane bro, I've got the UV at a slow enough rate that it should be achieving Level 1 Sterilization, possibly Level 2. I tried similar to what you described, but found I prefer to run a dedicated pump/line just for the UV, as I don't like my main return line flow rates being affected if I change the UV flow rate (or vice versa). Also both pumps are Jebao DC pumps with controllers, which makes adjusting flow rate even easier (though I also have some several manual control valves as you say within the system).

For targeted flow rates I'm using a chart from American Aquarium's UV Sterilizer pages: http://americanaquariumproducts.com/AquariumUVSterilization.html#turnover

Just of curiosity Duane, do you run your UV sterilizers 24/7 or sometimes turn them off?

 

[duanes]

When I used them, I ran the units at a very slow rate 24/7.
I was not concerned with free floating algae, my major concern was with pathogens, which need a very long detention time, enough to frappe their organelles.
And I may be a bit anal, because most of my UV training came in the form of seminars, for use in potable water treatment, "probably" a bit overboard for the normal aquarium .

 

[islandguy11]

When I used them, I ran the units at a very slow rate 24/7.
I was not concerned with free floating algae, my major concern was with pathogens, which need a very long detention time, enough to frappe their organelles.
And I may be a bit anal, because most of my UV training came in the form of seminars, for use in potable water treatment, "probably" a bit overboard for the normal aquarium .

Same here bro, no algae problems, just aiming to reduce pathogens. Currently the UV's on my 2 tanks' have flow rates that are about half way between Level 1 Sterilization and Level 2 -- basically I'm worried that if I slow it down enough to get a proper Level 2 like you had, that it might increase my water temperature -- and living on a tropical island that's an issue as my tanks are already both running about 84-86F day in day out.

But I guess the only way to find out for sure it to try It, while also monitoring the water temp closely.

Btw, may I ask why you are no longer using UV sterilizers?