The UV light in-line with my glass bead filter and high wattage pump does a good job of clearing green water when I leave it on full time. I just fired it up and had it going for less than two days and it has already begun clearing.
OK, understood.
Here is my problem: I believe I need a high wattage pump because ;
1. The filter intake is 3 feet below grade and the top of the waterfall it feeds is 6 feet above grade. Total head -- 9-10 feet
2. The intake is located 40 feet from the pump horizontally and the feed to the waterfall adds another 20 feet. Total 60 horizontal feet, equivalent to about 9 feet of head.
3. So total vertical head is about 20 feet and my current pump does the job.
However, the pump draws 11 amps @ 120 V which takes 32 Kwh per day. At about 18 c/kwh we have about $6/day.
If not for this cost issue, I could run this setup 24/7.
Hence my quest for a more efficient pump that has the necessary capacity.
Which triggered the thought that I might be able to put a UV light in-line with the pump that moves pond water into my big 2000 Gallon bog. That line is 1" diameter.
OK, I understand. Good to see your electric has dropped from 25 to 18 cents. That does seem more inline with what I'd expect in CT.
Two issues...
Your calculation on loss of head for 60' of horizontal run seems way, way off. You've unable to give any info that would enable even a rough estimate so here's just an example, a 60' horizontal run of PVC at 3000 gph would have the following head loss:
3" pipe = 0.4" head loss
2" pipe = 2.8" head loss
1.5" pipe = 11.5" head loss
1" pipe = 82.6" head loss
3/4" pipe = 335" head loss (basically the pump stops working)
Even a 1" pipe wouldn't be 9' of loss. But yeah, if you're paying an extra $1200 a year to save replacing undersized pipe with $40 worth of properly sized pipe I think I'd look at replacing the pipe.
Second, your focus on electric is pretty meaningless. The amount of electric only tells you how much you pay, not how much water is being moved. Without knowing basic info like pump GPH, size and type of pipe and UV flow rates you're totally in the dark and guessing.
The simplest solution would be to either move the existing UV light -- 2" PVC connections -- from the big pond filter and put it in-line with the bog pump with appropriate adapters to fit the 1" line.
My question then boils down to: Will the much reduced flow rate of the bog pump coupled with a fairly big wattage UV light do the trick?
No way to tell as you don't seem to know pump or UV flow rates or you're not sharing. I see you've been asked the question in the this thread but never responded at least that I could see. Kind of hard to help.
Does the flow rate matter much when it comes to sterilization? As long as the water flows at some rate and the UV zaps the algae should this not do the trick??
There's the issue. All UV filters are both a sterilizer and clarifier. Got it? Not some, not this or that model. All. Every single one. Manufactured or home made. All.
The only difference between a UV being a sterilizer or clarifier is the flow rate. Turn the flow down and at some point 99.9% of living things will be killed in one pass...that's a sterilizer. To clear green water it is not necessary to kill 99.9% of everything, microalgae is much easier to kill than some bugs. So water flow can be increased and then that exact same UV would be called a clarifier as long as water flow is still low enough to kill all microalgae for a given pond size. If water flow is increased further the UV does nothing and is called worthless.
PS: I would be quite happy if the 200 Watt pump you reference could push water 10 feet up and 60 feet across. Hence my interest in just locating a UV light closer to the pond -- in between the pond and the bog, minimizing both horizontal traverse and vertical head. At that point I either try to use the existing bog pump and put the UV light in-line or buy another pump of capacity sufficient to move water only 5-6 ft vertical and 15 feet horizontal which is much less that the load for the pump attached to the current pond filter location feeding the waterfall.
I think you're misunderstanding some things, but I'm not sure. Head is measured from the pond's surface to where water exits the pump pipe. If the pump is at the bottom of a 3' deep pond and pumps to a falls 4' above the pond surface the head is 4'. If the pump is at the bottom of a 20' deep pond the head is still 4'.
It doesn't matter how close or far the UV is from the pump, the flow is the same throughout the pipe. Unless the UV is way off on it's own for no apparent reason and you can reduce the total length of pipe. Then you can gain a little. But with proper sized pipe you'd be gaining fractions of an inch of head.
So they sell combination UV lights with attached pumps that I could try?
They do. I personally don't like them because it can be difficult to adjust the flow. The spec manufacturers give for clarifier is just an estimate for median ponds. Often water conditions make the UV less effective and the flow has to be turned down.
Saving money...
You're focused on using your 11 amp pump for some reason while at the same time being concerned about electric costs. Those 2 issues will never resolve themselves. There are only 2 ways to reduce electric cost. One, call the electric company and negotiate a lower rate...good luck. Two, switch to a pump that uses less electric.
A 60 watt UV connected to a 3000 gph 200 watt pump will clear a 6000 gal in less than a week. That's the bottom line. A 3000 gph pump for a 6000 gal is probably OK fish load wise, but you'd have to check that.
A waterfall is an entirely different issue. That's almost purely for aesthetic reasons...it is not needed to keep a pond clear or fish alive. If you want a tall falls with a lot of flow that costs money. A 4' head you lose about 1/3 of the pump flow (depends on kind of pump). But it could be turned off whenever you like, it's only for your enjoyment. There are other benefits to waterfalls, like bio filtering...but that's another subject.
O2 is added to the water by stirring the water. Waterfalls actually do a poor job of this. You will get more O2 by just having the pump stir the water. 0 head = more gph = more stirring.
You can also use air pumps instead. Although people think it's the bubbles it's really just the bubbles pushing water to the surface for gas exchange that make these work. Air pump use less electric to move the same amount of water as a water pump. That's why air pumps are used, cost saving. You could also choose to only turn on the air pumps at night, or when the water is warm.
For a UV to work it has to run 24/7, but maybe not forever. You also want to make sure it's installed correctly. They're often installed upside down and air gets trapped inside and they don't work as good.
So you could greatly reduce electric costs and increase water quality by selling the 11 amp monster on Craig's List and buying 2 or 3 pumps that solve specific needs. Each can be much lower power and only be used when needed.
I do think you're on the leading edge of what many more people will start to be concerned about in the future. Right now most people are OK with wasting $10 or $20 a month on electric. Too little an amount to bother with. But in the years to come, as electric gets into the 50 cents to a dollar range, that burning of $10 and $20 bills is going to be $50 to $200 a month up in smoke. Then there's going to be a lot more interest in how much electric a pond actually needs to use and "saving the planet" will go main stream.
