We live in Southern California ("SoCal"), where high electricity cost and koi ponds make for uneasy bedfellows. Under the San Diego Gas & Electric regime, we are charged per the following:
- 0 - 393 kWh, $0.27
- 394 - 1208 kWh, $0.48
- >1208 kWh, $0.55
Before making any changes, our total home usage averaged around 750 kilowatt-hours, well into second-tier pricing. I wanted to try out a shower filter because of all its claimed advantages, but also to keep electrical costs low. Before starting the conversion, total power usage for the moving-bed system was measured:
• Main pump, W. Lim, 375W (~ 7000 gph)
• Skimmer pump, W. Lim, 150W
• UV, 120W
• Aeration, moving bed, 80W
• Aeration, pond, 45W
Total: ~770W
(That means the pond along consumes about 3/4 of our total power usage)
So, how to reduce power?
The first step was to replace the largest consumer, the main pump. Say what you will about FlowFriend pumps–but the numbers don't lie*. Switching to the FF Pro reduced pump power from 375W to 70W (yes, 300W less), so the FF will pay for itself in about 27 months. Granted, FF pumps are only an advantage at very low head and/or high electricity cost. Total dynamic head was around 0.27 meters, or 11". With higher pumping head, the FF may well lose all its advantage, so be sure to run the numbers before considering one.
* Some people claim airlift setups will always be better than any pump. I can never tell whether they don't understand, or are purposely doing an apples-to-oranges comparison to arrive at their desired conclusion. Yes, air-lifts are superior - when lifting water 0 - 2", and perfectly suited for circulating water at high volume, but are completely out of their element when asked to actually lift water. To be blunt, an airlift cannot lift water 0.28 meters (11"), moving 7100gph, while consuming 70 Watts.
Shower filter supporters report all sorts of benefits, including:
- Superior filtration due to higher oxygen levels
- Off-gases ammonia (debated)
- Eliminates nitrite (debated)
- Eliminates nitrate (debated)
- Eliminates green water and the need for UV (debated)
- Makes you more attractive, definitely
I'm skeptical because of the lack of real data and the proponderence of wishful thinking, but was willing to give it a try to find out. To be fair, just because something isn't understood doesn't mean that it doesn't work, but the reasons why are important. A shower has a couple of other power-related advantages as well:
- Because the shower replaces the moving-bed, that aeration pump goes away as well, freeing up power.
- The UV may go away if the claimed benefits of the shower are true. If it can be eliminated, total power usage drops to around 350W, to less than half the original amount.
That said, even if the shower does have all the above benefits, it's not perfect because the system is at a much higher risk for failure:
- If the pump stops for whatever reason, the filter media immediately starts drying out at "some" rate. How long the bio film will last depends upon a number of factors, but it's likely to be in trouble within hours or a day at most. Once the pump starts back up, the pond will then experience a huge ammonia spike until the bio reestablishes itself.
- Shower media must be fed very clean water; if algae gets into it, it'll quickly plug up the pores. Some argue this isn't a problem, but I think it's a concern.
- #2 pretty much requires an RDF or sieve
- The sieve or RDF must be very reliable. If either fails, it'll quickly plug up the shower media. In comparison, a moving-bed setup will just passively sit there if the pump or RDF fails. Sure, some algae may get through, but as long as the air pump on the media keeps running, the bio will live for many days.
So, how to make a shower filter that's energy efficient? Shower filters are traditionally vertically-stacked trays, but I wondered, "why can't it be in parallel instead of series?" That is, instead of going tall, make it wide. About that same time I saw that Zac Penn was working along the same lines, manufacturing low-profile shower filters using large ceramic filter media blocks. Based upon these, I designed a low-profile unit that best fit my oddball space.
The basic box. Its odd shape fits its destination. The two ribs help structural integrity:
Unit was filled with a couple inches of water after being placed on our sloped driveway - no leaks!
Zac Penn's perforated media stands, with 1" clearance around each column:
With media test blocks to assess overall height:
How the media blocks stack up, which I also obtained from Zac:
Zac suggested this ultra-low profile water distribution system. Water comes in through a central 4" line and gets evenly distributed to 12 upturned ports (2" elbows cut down to further reduce head pressure). Each will have a perforated plate to further distribute the water evenly over each column.
Filling the unit with media
Done, for now. This shot shows why the unit is shaped the way it is. It hides somewhat behind the wall, and the offset also keeps the back end from hanging off backside of its platform. Still to do is adding the distribution plates, leveling the pipes, and plumbing the unit: