What size UV?

[randythawkins]

My pond will be about 1800 gal. which I plan on turning over once per hour. That 'once per hour' is what the pump will be doing. I will have a DB running to a SC and then to the pump. I will also have a skimmer running to a UV light and then to the same pump. I plan on regulating the flow of the skimmer line with a ball valve. Question is...what should the flow through the skimmer be (per hour). Seems like I need to know this so that I know what UV light to get (15W, 25W, 30W, ???). My brain is telling me I read that info many months back but can't remember nor can I find it again via google search. Can someone point me to a web page that would help?

Thanks,
Randy

 

[Dave 54]

We run a 36 watt one for our 1,000 gallon imperial so it cant be one much higher in power than that .

rgrds

Dave

 

[capewind]

Randy, the UV flow is decided by the brand in most cases. If I was building an 1800 gallon pond, this is the unit I would buy (but not from this site, you can get it cheaper) ....
http://www.emperoraquatics-pond.com/smart_uv_sterilizer.php#25watt

This is the one we are using on our next pond (under construction, will be between 4000-4500 gallons) http://www.emperoraquatics-pond.com/smart_uv_sterilizer.php#40watt

 

[cr8tivguy]

Question- If your UV isn't large enough, will it still work to rid your pond of algae (maybe just not as quickly)?

I have a hard time understanding how the UV system works. Basically, what I know is the water flows over the UV light and the algae and other bad things are neutralized. Anything other than that, I'm ignorant. What is the impact of 'too slow" or "too fast" water flow?
T

 

[capewind]

UV's have ratings from their manufacture. The "suggested" flow range will kill the algae and bacterias flowing through it, but if you are trying to kill protozoas, they then suggest a slower flow, as low as 15-20% of their typical suggested flow rate.

Size of UV to pond depends on what exactly you want the UV to do.

On our main pond, we are only running an 18 watt Emperor (already had it when we built this pond) ... should be running their 65 watt, but the 18 watt is doing what we want it to do, so no point in changing it,

 

[randythawkins]

Question- If your UV isn't large enough, will it still work to rid your pond of algae (maybe just not as quickly)?

I have a hard time understanding how the UV system works. Basically, what I know is the water flows over the UV light and the algae and other bad things are neutralized. Anything other than that, I'm ignorant. What is the impact of 'too slow" or "too fast" water flow?
T

My understanding is that...the brighter the light (more watts) the more it becomes a sterilizer killing bacteria and such while a lower wattage will just kill the floating algae. If the water flows too fast then then it is not exposed to the light long enough to get zapped. For my setup there is supposed to be a slower flow for the skimmer/UV line than for the bottom drain line and that will controlled via a ball valve. I read somewhere on what % of the overall flow should be run thru the UV but can't find that info now.

All that is from what I have been able to gather and understand so far. I could be wrong on bits of it.

 

[koiguy1969]

any U.V is a sterilizer or clarifier. dependIng on wattage and/or on flow rate. for an example...a 9 watt U.V is a clarifier at 1200gph, but at 300gph it can sterilize. as dwell time can accomodate for lower wattage. an 1800 gal pond can be kept clear with a 9 watt U.V. I INTENTIONALLY let my 1200gal pond green up bad every year.then clear it in 3-5 days with my 9 watt Tetrapond U.V.....
NOW,as a clarifier, the U.V is run to clear green water. once accomplished, it can be shut off and even removed from the system. as a sterilizer it's usually ran all season, even when the green water (single cell algea) is gone.. but this is to kill protozoans, parasites, and other pathogens. i run 865gph thru my U.V. when my water is clear, i run the U.V for an additional week or so. then i disconnect , clean, and store it away. till the next year. and my water stays clear all season.. and i've used the same bulb for 6 years.

 

[randythawkins]

koiguy1969 - you said what I need to hear. Thanks.

 

[koiguy1969]

koiguy1969 - you said what I need to hear. Thanks.

thats NOT to say that you wouldnt be better off with a larger model... an 18 watter. at twice the watts means it should be about twice as effective at the same flow rate. your better off being "bigger than neccessary" than "too small"

 

[randythawkins]

thats NOT to say that you wouldnt be better off with a larger model... an 18 watter. at twice the watts means it should be about twice as effective at the same flow rate.

gotcha

 

[JPpondxperience]

So do you guys think is over kill to put a 55W UV on a lets say 650 gallons pond? I'm picking up a brand new Laguna 55W UV for $100 from someone that purchased it and never used it and now is trying to get rid off it so is there such a thing as too much UV light, I'm not planing on running it all the time, just for a week or so and then until the water starts to get green.
Tks.

 

[koiguy1969]

A 9 watt U.V is more than adequate for a 650 gal pond... my 1200 gal pond clears in a few days with a 9 watt.... a 55 watter will do a great job. if the price is right, why not?

 

[JPpondxperience]

Great, thanks for the advice, I actually went and picked the U.V today, brand new Laguna 55W for $100, I wanted to install it tomorrow but the wife had other plans so I guess it'll be Sunday, my water is getting very dark right now so I think I'll take a picture to do a before and after installing the U.V.

 

[Dave 54]

Dont forget it goes in after your filtration (some folks make that mistake believe it or not).
Ours is 38 watts and it does 1,000 gallons UK with ease it has a two year bulb life span not the one year ....
Properly maintained with the cystle sleave rmoved from time to time to be cleaned on the outside .
Its also an idea to check the rubber seals as well.
Keep it up and it will last you a lifetime.


rgrds


Dave

 

[koiguy1969]

DAVE54 .. you cant install a U.V after the filter with a sumersable pump, and gravity return system. my U.V is installed before my filter, and works great. its only ( watts and will clear my pond in 3 - 5 days. i only run it 10 days a year. clear the pond and an extra week for good measure. i take it out of the system clean it, and store it away for the next season. used the same bulb 6 years. a presure filter with a submersable pump. i would suggest using a prefilter as i do. thats an "inpond" mechanical filter before your pump.

 

[Dave 54]

Koiguy69 I was talking non submersable filter , I keep forgetting many of the ponds on this site are rigged up this way .
You are indeed correct as thats the way our QT system is laid out, however UV-C s are meant to be run 24/7 365 days a year...
We use the double bulb U/V-C and they only last the 2 years before they need replacing loosing half their power in a year poof of this was when I forgot to replace ours and ended up with a green pond, so I now diligently change them in the spring every 2 years.

rgrds

Dave

 

[koiguy1969]

wow... some editing is neccessary on my last post.... that should read 9 watts, not "( watts." and "you should plumb a U.V after a pressure filter." my keyboard batteries must be getting low.
and my filtration is external...i just run a prefilter, before my pump to trap solids before clogging my pump or getting pureed into poop soup and sent to biofilter... but my filter is a DIY upflow waterfall box (SKIPPY STYLE) and the water returns to pond, via a weir,or spillway (gravity flow) ..not tubing under pressure. a U.V would restrict flow and cause filter overflow!!
and YES, my U.V still works... i only run it about 10 days a year. So in 6 years its got 60 days or 2 months use!!! bulbs are rated in hours. mine is rated about 9000 hours. or 8 months.of use then they start loosing effectivenmess.
A U.V only needs to be ran 24/7/365 if your using it for sterilization, "parasite and pathogen control"... on a unplanted formal koi pond yes..on a garden pond with koi as a clarifier, or "just green water alge control"....not neccessarily, once the single cell alge is dead,& green water gone, no need to run it. my water remains clear all season.

 

[slyman]

This is just the thread I was looking for. I have a small 450 GL pond with a Pondmaster 3200GPH pump going to my waterfall. I know for the size of my pond I don't need a lot of wattage, but do I have to get one big enough to handle the pump output? My plan would be to cut the 1.5 inch line going from the skimmer to the water fall and install it in-line. Would that be the correct way to install it? I had one on my last pond but it was in a Savio skimmer, so it was so easy. I miss that skimmer. Thank you.

Bob

 

[crsublette]

I think there is a misunderstanding in that folk think pond volume determines the UV size and wattage. This is not correct.

Pond flow rate is what determines the UV's size and wattage and effectiveness.

Flow rate alone does not determine if the UV is a sterilizer. The strength of the UV light spectrum is what matters when talking about being a sterilizer to kill pathogens, virus, and parasites. Here is a thread, from AquaticEco about sterilizers, that talks more about what is needed to make a UV into a sterilizer.

The diameter of the UV pipe matters as well. UV light can penetrate water as deep as three inches. So, eventhough a 1" flow of water through the UV works fine, you will get the most bang for your buck with a 3" flow of water through the UV.

How do I choose my UV ?? This is a tough subject since there is no easy way to talk flow rates without metering the water, but you can take a rough guess by looking at your pump's flow rate, do some head/friction loss calculations, and then determine your actual flow rate. When properly installed, the single cell pea soup algae should clear within around a week or sooner; so, if this has not been achieved, then slow the flow rate of water with a valve prior to the UV.

For the UV to be a sterilizer with the proper light strength, then the flow rate is approximately 10~20 gph per UV watt rating. So, for a 9 watt UV to be a sterilizer, assuming it has not lost any of its light strength, then the flow rate should be around 90~180gph through this UV.

UV is a sterilizer when it attempts to obtain a 90~100% kill rate of everything in the water that passes by the light.

UV is a clarifier whenever it obtains a much lower kill rate. A kill rate just long enough to kill the single cell algae and I don't know what this kill rate would be to accomplish this.

From reading folk's testimonials, it seems a flow rate of anywhere between 50~100 gph per UV watt rating is enough, but, ultimately, this is told to you by the manufactuer's product flow chart. Although, I have seen the flow rate being anywhere from 40~120gph per UV watt rate, but some folk seem to do just fine with a higher flow rate although it might take longer to obtain the results they desire.

The two brands I highly recommend, due to other professionals that I know who use them, are Evolution Aqua evoUV and Emperor Aquatics. Often times, the more profesional pond hobbyists will have multiple UVs, either multiple 55watt or multiple 110watt, units in parallel so they can significantly improve their flow rate.

Ultimately, choosing your UV depends on your flow rate and what type of flow rate you want to have while effectively using a UV.

 

[crsublette]

This is just the thread I was looking for. I have a small 450 GL pond with a Pondmaster 3200GPH pump going to my waterfall. I know for the size of my pond I don't need a lot of wattage, but do I have to get one big enough to handle the pump output? My plan would be to cut the 1.5 inch line going from the skimmer to the water fall and install it in-line. Would that be the correct way to install it? I had one on my last pond but it was in a Savio skimmer, so it was so easy. I miss that skimmer. Thank you.

Bob

There seems to be a debate on if an inline UV is more effective or if a bypass for a UV is more effective. I say it depends on the convenience of the owner since what matters is to make sure the flow rate is correctly matched with the UV to accomplish what you want it to accomplish.

For a 3200gph pump, with I imagine there is some flow rate loss due to friction and head loss, then the actual flow rate is likely lower than 3200gph unless your pump has a high head height ability. So, assuming there is no flow rate loss, then, for the UV to be a clarifier that is around 50~100 gph per UV watt rating, then a 32~64 watt UV might work for a flow rate of 3200gph, but I would follow the manufacturers recommendation whenever you do choose a UV device. This is just to give you a starting point.

If you want to create a flow bypass to use only half of that 3200gph flow rate for the UV, then a UV clarifier for a 1600gph flow rate would around 16~32 watt UV. Again, I would follow the manufacturers recommendations whenever you do choose a UV device since it also depends on the UV's light spectrum and how it is built. This is just to give you a starting point.