Multiple UV units, Series or Parallel.

[acroporas]

When hooking up multiple UV units on a one system, which is more effective: Series or Parallel. I define effectiveness for a UV unit (or combination of units) as the maximum rate in which water can pass through the units and kill the target organism.

Let us assume that we have a UV unit that is capable of killing the target organism at a rate of 500GPH.

When two are hooked up in parallel, the math is easy. You get a total of 1000 GPH which can pass through the combined UV system.

But what about two units in series? Would the max flow rate be > or < 1000GPH?

Obviously setting them up parallel has the advantage of having less head so it is easier on your pump. But if you can sterilize more water with them attached in series it may be worth it.

 

[adambaron]

I would think you would still probably have to stay around 500 gph but it would kill slightly more. Although I do imagine it is asymptotic and would only be slightly higher than a single unit. Just my thoughts though.

 

[cchoffman]

I would think if you got the correct size, you would only need one.

 

[silverwolf72]

500 gal/hr for parallel or 1000 gal/hr for series both of these will have the same contact time with the UV light

 

[TekCat]

splitting them in parallel makes more sense to me: first of all contact time will be contiguous, instead of having to be interrupted when water goes from one unit into another. second, it provides easier maintanance scheme: when need to work on one UV, you'd just disconnect it, while having water still moving through the system via second UV path.

...jmo

 

[Randall_James]

sort of depends on what you are trying to kill, UV is all about "dwell" time. It takes X amount of exposure for X mass. An organism that dies in a "series" setup may very well pass through a "parallel" setup untouched. If you could guarantee that the units flowed identical, you could in theory run parallel and get the same exposure. I just do not think you can get that to happen very easy is all.

I think I would just go with one "bigger" unit myself

 

[billsreef]

There's a reason all the large multiple sterilizer units that are commercially available have them set up in parallel. If a given unit is rated to kill parasites at 500 gph, it will not work when pushed to 1000 gph, even if you put two of the same units in series as each unit will have the water flowing faster than it is designed for. In fact just from a plumbing standpoint alone, the unit might not even be capable of handling the increased flow. When set up in parallel, you can run 500 gph through each of two units rated for 500 gph and you will have a total flow of 1000 gph that has been subject to the proper killing dose.

 

[acroporas]

Thanks for the help guys. You are right that big units are all set up in parallel. I guess I could just trust that they are doing things right but that's not how I like to do things.

I desided to quit being lazy and get out my books and do the math. It looks like to me that there is no difference from a kill-factor point of view.

Since there does not look like there is any advantage to running them in series and there are obvious drawbacks (lots of friction) I guess I'll be pluming them in parallel...