Improving my overflow rain barrel

Long ago I stuck a barrel under my deck and called it my over flow rain barrel.  I put a float valve near the top of the barrel so it would fill when the water in my other barrels was above its height.  I installed a hose bib lower on the barrel, attached a check valve to it, and plumbed it back into the tubing that connected the rest of the barrels.  This worked well, but there was room for improvement.

Overflow barrel in relation to the nearest rain barrel.  It's 8-10" lower.

Closeup photo of the overflow barrel under the deck.

The first problem was that this overflow barrel only filled when the water in other barrels got to a level higher than the overflow barrel.  That's not a huge deal, but when it rains hard the barrels fill fast.  The water then goes out the overflow on the barrel and doesn't make its way into the overflow barrel.  This is due to pipe sizes.  The tubing going from the main rain barrel to the overflow rain barrel is only 1/2".  Water moves rather slowly through it.  The overflow on the main rain barrel is 3/4".  

The second issue is getting water out of the overflow barrel.  The hose bib is 12" up from the bottom.  That meant that there was a foot of water in there that I couldn't get out.  It was unusable.  This also made moving the barrel out from under the deck very difficult.  (I like to check it once a year to make sure nothing is growing inside.)

My improvement started by moving the float valve from the top of the barrel to where the hose bib had been.

Float valve installed at the hose bib location with strainer attached.

Then I added a long chain to the float. I've always used these float valves with the float directly attached to the valve.  I wasn't even sure that adding a long chain would work.

Initially I took a guess as to how much chain to use.

Next I had to address the issue of getting the water out of the barrel.  I decided that in order to get the most out of the barrel that I would have to put a drain in the bottom.  I drilled a hole and installed a Uniseal bulkhead adapter.

Then I inserted 1/2" PVC pipe and attached a hose valve to it.

Then came the big test.  I put the barrel on some blocks since it could no longer sit flat on the ground.  Then I filled it with water to check for leaks and verify that the float valve would work in the new location.

Success!  The float valve worked just fine.

Once I was convince that the barrel would work this way I had to empty it.  I didn't want to waste the water, so I used my pump (not pictured) to move it into another rain barrel.

I had some concern about the chain on the float getting tangled by repeatedly draining and filling the barrel.  To lessen this possibility I added a short section of chain to the float and attached it to the top of the barrel. 

The last step was to put the overflow barrel back under the deck.  I connected it to the nearest barrel with some drip irrigation tubing.  Eventually I'll tie it into the tubing under the deck that connects the rest of the barrels together.

The final thing I did was to add a short piece of clear tubing that would show me the level of the water in the barrel.

I've been real pleased with how this has turned out.  The barrel fills sooner since the intake is lower, and I'm able to completely drain it.  Eventually I'd like to expand my water storage capacity by adding several more barrels under the deck.