Wednesday, May 29, 2019

rain barrels 2

Barrel equalization with a siphon bridge and flood control continued

rain barrels part 1

Lessons learned: This is a former rain barrel setup where I had re-used three food grade barrels on a raised platform behind a pool shed/pump house. The location was ideal, steps away from a large (5m x 10m) vegetable garden. The edge of my solar pool heater array can be seen at left back.

Using only rain water my three barrels were adequate to spot-water my garden over several hot summers without diverting the pool waste water. I used a watering can, not a hose. Better exercise and water control.

The two downspouts delivered all the rain water from the shed roof into the outer barrels.

I considered diverting some of the waste water from cleaning the pool sand filter (the single white pipe lower right) into the barrels. The high flow rate of the waste water made it difficult. I had once measured the flow rate as 37 gallons per minute. There was no "low" setting for the pump and 50000 gallons of water available in the pool. Better to just let it blast out into the seasonal stream. The wastewater pipe extended about 5 meters from the shed toward the stream.

So diversion of the pool waste water was not really required. But some of the details of that system could have been improved.

Covers on the barrels prevented insects from entering and laying eggs (like mosquitoes). Some designs have a screen at the top of the barrel. Any debris from the roof would have to be cleared regularly from this screen. That sounded like a bad idea.

Here, rainfall via the downspouts dropped straight into the barrels through tight seals in the covers, keeping insects out. But was not a good idea for a couple of reasons.

Any debris from the roof went directly into the barrels. By the end of the season, there was a thick bed in the bottom of the outer barrels, enough to clog the equalizer hoses.

There was no provision for overflow. During torrential rain a small lake would form at the back of the pool shed from the water that overflowed the barrels. Next to the house this might cause water to enter the basement or saturate the foundation. But behind the pool shed this wasn't a serious problem.

The single tap was on the center barrel. I had used a fancy and expensive bulkhead valve from Lee Valley Tools, so there was only one tap from which to draw water from three barrels.

I needed a way for the water to flow between the barrels, as new water was added to the outside or as I took water from the center tap. You can see my solution in this picture [click any pic to enlarge]. I used Carlon electrical fittings and short lengths of garden hose to connect the three barrels at about the same level as the tap. The tap height establishes the lowest level that the water can be in the barrels so the equalizing hose should be at the same level so all three tanks drain equally.

If the equalizer hoses or the tap are up on the barrel somewhere, not at the bottom, you won't be making full use of your barrel capacity.

A barrel should be raised off the ground, at least as high as the top of your watering can, or higher.

Back to here and now: I have re-arranged my two 55 gal re-cycled food grade barrels to be at one end of the roof rather than one at each end. I want to do some work on the other end of the wall so that barrel had to be moved. I have adjusted the trough on the roof edge to slope downward to this corner rather than down from the center so all the water now flows to this corner.

I have a single diverter (at the green arrow - the Canadian made "Catch-A-Raindrop" described in part 1) in the downspout to the ground and a single fill pipe to the left barrel. The downspout sends overflow into a drainage ditch to get the water further from the foundation. The diverter will not send water into the barrel when it is full. Leaves and debris from the roof continue to the ditch. It works great!

But it only feeds one barrel while maintaining auto shutoff to prevent overflow.

I needed a way to equalize the level in two barrels. I could have used the same arrangement as I did above but instead I decided to try a siphon bridge.

My siphon bridge is a length of hose which reaches the bottoms of both barrels. Primed with water (no air inside) the siphon bridge will allow water to flow from the barrel with higher water level into the barrel less full. I am using PEX.

Here I am demonstrating to myself that the concept does indeed work. The right barrel had been about a foot lower in level. After about 1/2 hour, the two barrels equalized.

The siphon bridge was attractive because I didn't have to put any new holes in the barrels. I had already emptied, cleaned and refilled them. To accommodate the siphon bridge needed two pipe sized holes drilled in the barrel lids.

The final configuration with both barrels full and ready. The blue arrow shows the siphon bridge in place. The yellow arrows show the tips of the water level gauges.

Note that insects have no way to enter the water. The tops of the barrels are essentially sealed although some air can enter as water leaves the barrels.

I suppose the siphon bridge could be used to connect three or more barrels.

Although simple, the siphon bridge needs to be primed. This means sucking the air out. I used my mouth on one end, holding the other end deep in one barrel. I held it low to the ground to ensure that water was flowing at a good clip and then closed the end with my thumb and stuck it underwater in the other barrel.

It was necessary to have the PEX already inserted through the covers so they could be screwed down once the siphon was primed.

The siphon bridge has the disadvantage that it needs priming and it might again if it looses prime. The horizontal tube at the bottom approach does not require priming but it is more complex and needs more holes in the barrels.

rain barrels part 1

Interesting video of siphon bridge used between two raft beds.

Thanks for your interest.

George Plhak
Lions Head, Ontario, Canada

As before, not wanting to pick on Home Hardware. This is a current example of a popular rain barrel product with an insect screen at the top. Roof debris would clog this filter unless cleaned regularly. No overflow consideration. With tap at the bottom of the barrel you'd get more water out if the barrel was raised off the ground, at least as high as the watering can filler. Not sure how you would cascade two or more of these if you wanted more capacity.

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