UV flow rate

[RandyC]

Not to gotcha you, but if it's two pumps each putting out 300gph or a single 600gph pump going in parallel to two UVs, that's the same no? Both are just different mechanical configurations of the water routing.

RE the sizing and what not, maybe I'm misinterpreting the original post, but I assumed it's two equal sized and the only difference is plumbing configuration. Everything held fixed my vibe being both configurations seen equivalent. As long as you don't do crazy town and do 2-600gph separate pumps versus a single 600gph. That definitely would be worse, because total dwell time is halved.

Said differently, ignoring some details, I'm proposing these seem equivalent (600gph being arbitrary):

1. A serial, setup with 2 UV and a 600gph pump
2. A single 600gph pump connected tee-ed to 2 parallel UVs
3. Two separate 300gph pumps powering 2 separate UVs

I originally thought the double 300gph would be better, but I don't think the math works out that way. Given that I think the answer is "doesn't matter", and whichever is easier to plumb and do maintenance on.

yes, in theory all three of those are the same from a dwell time perspective. Having two in parallel could avoid unnecessary (potentially small) complications.

However:

1. maintenance is not the same
2. Need to ensure that the correct flow for both UV units vs. one if done in series
3. Chance (though probably small) of having just UV treated water immediately go into the other UV unit vs "new water" lowering turnover rate

 

[JVU]

Not to gotcha you, but if it's two pumps each putting out 300gph or a single 600gph pump going in parallel to two UVs, that's the same no? Both are just different mechanical configurations of the water routing.

RE the sizing and what not, maybe I'm misinterpreting the original post, but I assumed it's two equal sized and the only difference is plumbing configuration. Everything held fixed my vibe being both configurations seen equivalent. As long as you don't do crazy town and do 2-600gph separate pumps versus a single 600gph. That definitely would be worse, because total dwell time is halved.

Said differently, ignoring some details, I'm proposing these seem equivalent (600gph being arbitrary):

1. A serial, setup with 2 UV and a 600gph pump
2. A single 600gph pump connected tee-ed to 2 parallel UVs
3. Two separate 300gph pumps powering 2 separate UVs

I originally thought the double 300gph would be better, but I don't think the math works out that way. Given that I think the answer is "doesn't matter", and whichever is easier to plumb and do maintenance on.

Don’t worry you aren’t gotcha-ing me, because I think you are saying the same thing I started with, that they are functionally about the same.

Since you were getting into it with diagrams and math and stuff I was just pointing out that having 2 units in 1 system is different than 2 systems if you want to be a bit picky because of mixing effects between systems. But for the purposes of killing stuff with UV they are functionally about the same.

Also just practically speaking I agree with you that keeping it simple or having it work with existing plumbing will be more important to an individual reefer.

 

[MichaelB]

One of the best studies and longest Ive read on Cryptocaryon irritans ( marine ich) a while back was by Colorni and Burgess 1997 which was an extremely lengthy phd research paper! I could not find that research paper but this article in the link sources some of their studies as well as other research papers on the subject.
Whats notable is fish can be asymptomatic of marine ich acting like carriers with no symptoms for 6 month or so when a new clean fish is added that one can develop ich immediately . They hatch mostly at night from the sand and rocks while most fish are laying their sleeping so easy prey..They do talk a bit regarding Uv
Anyhow good read enjoy!

FA164/FA164: Cryptocaryon irritans Infections (Marine White Spot Disease) in Fish

University of Florida, Institute of Food and Agricultural Sciences Extension outreach is a partnership between state, federal, and county governments to provide scientific knowledge and expertise to the public. The University of Florida (UF), together with Florida A&M University (FAMU)...

edis.ifas.ufl.edu

Good information. Also understandabe being a plus.

 

[richiev]

A couple interesting points ChatGPT in research mode found regarding the potential benefits of parallel:

• Pro: Flexible Targeting (Algae and Parasites): One interesting use of parallel UVs is to dedicate each to a different purpose. For instance, you could run one unit with a high flow (fast turnover) to clear algae and bacterial bloom issues, and run the second unit with a much slower flow to target parasites. This way, you are simultaneously addressing both concerns: the tank water stays clear and you’re also continuously chipping away at any ich/velvet in the water. Bulk Reef Supply even suggests that running two return pumps in parallel – one tuned for algae, one for parasites, each with its own UV – is “the way to go” if ultimate protection is the goalbulkreefsupply.com. It effectively gives you a broad-spectrum approach: one UV is a “clarifier”, the other a “sterilizer”. In a single-UV scenario, you’d have to pick one flow setting or compromise in the middle (which might not fully optimize either goal)reef2reef.com. Parallel lets you optimize each independently. Do note, as discussed earlier, that water from the “fast” line won’t get the parasite treatment unless it later mixes and goes through the slow line, so this method is best if you have strong circulation ensuring all water eventually passes through both over time.
• Pro: Easier Maintenance and Redundancy: With parallel UV units, you can usually take one offline for maintenance without stopping flow to the tank. By closing a valve on one branch, all water can be temporarily diverted through the other UV (or through a bypass) while you change a bulb or clean the sleeve on the first. This means you don’t have to turn off your return pump or filtration – your tank still gets circulation (and some UV sterilization) during maintenance. In series, as mentioned, you’d need a special bypass or have to turn off flow. Additionally, if one UV unit fails (leaks, lamp dies, etc.), you still have the other one running. The system won’t be as effective, but something is better than nothing. Parallel setups can thus be more fault-tolerant. Some reefers with critical tanks run dual UVs for peace of mind – if one goes down, the second unit can temporarily carry some load until the issue is fixed. Also, running two identical units means each one might be under less strain, potentially extending their life (though UV bulbs typically just age by hours on, not by how hard water flows).
• Pro: Lower Head Pressure (Pump Friendly): Splitting flow into two paths reduces the resistance in each path. Your pump doesn’t have to force all water through a single narrow UV tube. As a result, you often see less drop in flow with two parallel UVs than you would pushing the same total flow through one big UVreefcentral.com. In practical terms, this might allow you to use a slightly smaller pump or save some energy. It also means if one UV clogs or accumulates debris, the other can still flow, preventing a huge pressure buildup. Overall, parallel plumbing is gentler on pumps and can be tuned such that each UV’s flow is just right without overworking the system.

Here's the full result, but note that it seems to not be grok'ing the idea that in parallel the proposal was run the flow at half speed, so it's giving incorrect info about the dwell time.

Still seems like "meh", either way, unless you were to do something like run one on a return line at high volume killing algae, and then a second as a low-gph, high dwell time, parasite killer.