Koi pond 2010, Okay your two 90 degree elbows equal 16 ft of 3" pipe. I assume that you may use a bulkhead fitting and each of those will add to the length of the pipe. Then all the fittings connecting to the bulkhead will add to the pipe length. Also the fact that water is going from a large area to a pipe and then back to a larger volume adds to the length of the pipe. You could easily get to 30 or 40 ft of 3" pipe. At 30 ft the SC will drop about 2 inches at 2400 gph and at 40 ft it will drop about 2.5 inches. Now looking at the possible air bubble entrapment. Air bubbles are trapped either at elbows or in horizontal runs of pipe that have a high point in the center of the run. The way to fix these problems is the elbows coming out of the filter are replaced with a tee with the through branch of the tee being vertical. The highest end of this tee is left open to the air so that any air inside the pipe can get out. Any elbow that does not turn the water to a downward direction is not problem. The other place you can have a problem with an elbow is where it empties into the pond. If the elbow is on the pond side of the edge of the liner then a small hole can be drilled in the top of the bend of the elbow and the air will bleed off. If water comes out this hole it will flow into the pond. If it is not in this position then it becomes more complicated but can be done. On the tee installation a small piece of pipe may have to be put in the open end to keep the possibility of water coming out. Mike

I second zendog. The pipe size needed can be computed but you need to know the pump's GPH and length of pipe, size and fittings. There are friction tables and calculators online. That gives you the amount of water entering the first barrel. Or you can test directly using a stop watch to see how long it takes to fill a 5 gal bucket or both 55 gal barrels if the media is removed. Once you know the speed of water coming in you can compute the size pipe needed to keep up using gravity. Not as complex as it sounds, but does take some noddling. A lot less work imo than trying different sizes. 3" from barrel 1 to barrel 2 would be a good guess, but you might be able to get away with 2". It throws a lot of people but a 2" pipe is a bit more than 3 times the area as a 1.25" pipe and a 3" has over 7 times the area. Another problem you may run into is called draw down. It means when this is running the water level in the 1st barrel will always be higher than in the 2nd barrel. So the out flow in the 2nd barrel has to be a bit lower than expected or the 1st barrel will overflow. This draw down thing get worst as more barrels are added in a series. The best way to deal with it is to put the pipe thru the barrel much lower than needed and then 90 to vertical. The water overflows into the vertical which is easier to adjust up and down. Once an an outflow is drilled too high you're kind of screwed. If I might make a couple of suggestions. First is the type of filter you're trying to make is submerged media meaning the media is always submerged. These are very poor filters and are pretty much impossible to use because the media clogs and the filters overflow. So at the very least you really need a separate overflow on each barrel to handle that case or you risk emptying the pond depending on where your pump intake is located. This is a very old style filter and modern filters have been tested to perform around 30 times better for ammonia removal. Mainly this is due to increased gas exchange (more O2). But also because submerged media conversion of ammonia gets less and less as the media clogs. Which means lots of cleaning to keep up conversion. Cleaning 55 gals of lava rock is no fun at all. Modern filters are self cleaning. Trickle Towers were the first of these modern filters. Moving Bed (aka fluidized bed) and Bakki Shower came next. You could convert your barrels to these much better designs pretty easily. To convert to Trickle Tower you raise the barrel up so the bottom of the barrel is above the pond water level. Water comes into the top and washes over the lava rock. It's like a water fall inside a barrel. The washing keep a lot of muck from collecting and gives the bacteria max O2. You'd split the 1.25 pump line so 1/2 goes into each barrel. It is much more efficient running these in parallel than in series. The next option to turn one barrel into a moving bed. You would have to buy media for this which is a little pricey but there are DIY substitutes. Conversion means placing a plastic grate at the bottom of the barrel to keep the media from flowing out. Then the water form the pump is directed downward into the barrel near the side of the barrel, That causes the media to roll. That keeps the media washed 24/7 and lots of O2. Lots of DIY ideas on the web, A shower filter would be more difficult and they are noisy. But if interested there are lots of DIY instructions around the web. It is very unfortunate that there are still lots of people pushing these old style submerged media filters. But that's the web for you...99% junk info. These newer filters are worth checking out as they will be much easier to build and perform so much better.

Hi squid, It is a good thing for the barrels to be at the same height and linked to act as one large reservoir. Your barrel are about 4 feet high that empty to within 18" of the bottom. That gives you 33 gallons per barrel for 132 total gallons. The pressure in psi is equal to approximately 1/2 the height elevation difference (in Ft) of water. Your closest run would have 2.5 psi of average pressure and with level tape run. Your longest run has 3 psi with about 1 psi gain along the run. The ideal run of drip tube to keep pressure even along the run is about 1.5% slope. Your longest run has 18" drop over 24 feet that is about 6% slope which should make the last part of the tape push more water that the beginning. For drip tape higher pressure would be better for uniformity and use of water. Something in the 2 gpm or 120 gph range would be a hobby or aquarium pump by Eheim. They have In-Line pumps that can be used as submersibles as well. I have never used these pumps but found them on Google. It would take you about 66 minutes to use up your 132 gal supply. Remember to filter. Be careful about supplementing Municipal water to your barrels chlorine would kill your fish. Thanks for the added info that made the picture clear. Aloha.

I bought mine from By The Barrel in Minneapolis (its made from an old wine barrel) and they suggested to redirect your downspout away from the barrel, cover it in plastic, and leave the spigot open. Left it out all winter with no problems. I've had plastic ones blow the bottom out before. The wood on this one is like an inch or more thick, so I don't see that being a problem! I think their website is www.bythebarrelmn.com. If not just google them! They were great to work with and very helpful. Plus they are made rigth in this guy's garage in Minneapolis.