Hi,
I'm not sure if when you tested it you had any filter media in place or whether it was just empty barrels, but that will have some impact on flow. So if you tested it without media, the flow will be less when you add media. And if you tested with media, the flow will decrease from there as well as debris builds up in the media, etc. And of course, the type of media will impact it as well.

Regardless, you are dealing with a water pressure inequality issue and probably the easiest way to fix it quickly will be by changing the size of some of the hoses.

Basically, when the water comes out of the pump it is under pressure - that is why it can basically go uphill. I don't know how much pressure, since that is probably some complicated math based on the size of the pump, the head, length of hose (friction from the sides), etc.

But the water flowing from the first barrel to the next is only being drawn by the weight of the water and gravity. So while the hose is the same diameter, it will be flowing at a much slower velocity than the one under pressure from the pump. Therefore the barrel is emptying slower than it is filling and will overflow.

Probably the easiest way to fix this is to increase the size of the hose from the first barrel to the second and from the second barrel to the falls. But how much, is of course the question. Others who have built similar systems may have an easy answer for you, but without that, the easiest way is to take off the existing hose from the first barrel to the second, remove any fittings at the site of the attachment and then try pumping water again with the water just going out the hole. That existing hole without the fittings should be bigger, so if that does it, then you just need to redo your fittings and pipe so that the minimum internal diameter slightly larger than whatever size that hole is. I say larger, since you want to allow for some friction from the hoses as well as some future slowing of flow into the second barrel as the media starts to collect debris. If it was me, I'd probably like to have the internal diameter of the hose be big enough so that you could always see the top 1/4 or so of the exit hole above the water when viewing the barrel from the inside. And if you still have overflow based on the existing hole you orignally had for the current fittings, then you'll need to make the hole bigger, test again, repeat again if it still overflows, etc. In general, I believe you will want to oversize your exit tubing to allow for increased resistance to water flow in the second barrel if, for instance, sometime you clean out the first barrel but don't touch the second so that you don't mess with the bacteria bed in both at the same time...

At least that is how I see it based on your description.

Good luck

Thank you for your input on this, Zendog. When we tested it, we only had lava rock in both barrels. I was planning to add mechanical filter media, such as the blue a/c filters, quilt batting, and other materials on top of the lava rock, but now I'm not sure if that will hinder or help.

Hi,

I think you'll need to balance out the difference in water pressure/flow rate either way. But you may want to put in the material you plan to ultimately use if you test as I mention above, since things like quilt batting can slow the water flow substantially as they fill with debris. Ultimately it comes down to needing to have the water flow out of the first barrel faster than it comes in, which won't happen with the same size hoses and just gravity taking it to the second barrel and out to the falls. With the same size hoses the only way to make it work would be to restrict the flow into the first barrel with a valve on the inflow pipe (thereby reducing your water pressure), but that will ultimately cut your overall flow and I don't think you'll be happy with your waterfall or your overall filtration since you won't be moving as much water through the filter.

One other consideration is relative height of the inflow and outflow. If, for instance, you had the first barrel significantly higher than second, the added weight of the water that was physically above the outflow from the second barrel will build more pressure on the outflow - the same idea of pumping water into a water tower to pressurize the lines to homes. Another way to increase the differential between inflow height and outflow would be to take the water out of the second barrel lower down, say around half way up the second barrel instead of up near the top.

There is a chance that might give you enough difference in pressure since half a barrel of water above that would weigh quite a bit and might give you enough velocity on the outbound tube. But you'd have to test that and might still need to go to a bigger outflow, and of course you will have lost half a barrel of filtration.

If it was me, I would probably jump right up to at something like 3" pipe from the first barrel to the second and out to the falls. But I know it is much harder to hide a bigger pipe than it is to snake a nice 1" black tube behind some rocks... The other advantage of a wider outflow is that it is less likely to get clogged if somehow a bunch of muck works its way into the system over time.

Let us know how it works out.

p.s. As an amendment to the test I suggest above, I should say that when you monitor outflow with just the hole open you need to make sure the water doesn't go up higher than the hole, not that that it shouldn't overflow.

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.

Thanks waterbug guy. You've given me a lot to think about. I'm familiar with trickle towers. I have a small one running at the edge of the pond. A large flower pot with lava rock. If I made the barrels into trickle towers, wouldn't I still need a mechanical filter?

Mechanical filter are entirely different and really should never be combined with bio. It just makes both into crap. Mechanical is more complex. Really depends on your desired goals. If the goal is the clearest water and lowest DOCs because you have a high fish load you want a UV filter to kill algae. Then you want a bottom drain system that includes TRPs to push crap to the drain and something like a sieve that removes chunks of crap 24/7. Then a Sand & Gravel or fabric filter for getting the finer stuff. The idea is to remove bigger stuff before it decomposes into millions of tiny bits. Tiny is more difficult.

If your goal is just keeping the pond kind of clean so it doesn't fill with muck I think a simple vacuum system is way easier than filters and more effective for Water Gardens. Filters sound good but are way more difficult than a few pads that are hyped in hobby forums. People clean pads and see a bunch of dirty water and think wow this thing really works. But that's a tiny amount compared to what collects in the bottom of the pond.