Letter Re: An Inexpensive Approach to Underground Rainwater Storage

I know that you have had stuff on about rain harvesting over the years. I thought I would add my $0.02 worth. I live in a dry climate in the west. We’ve had many fires this summer so water is an issue here. We get rain in the summer, but it can be sporadic and voluminous when it does come. So, in order to even things out I wanted to be able to capture some of it for future use. I was trying to figure out how to do it inexpensively. I wanted to bury whatever I did for reasons of OPSEC and also because it freezes here and I want to be able to store water throughout the year. I looked at a lot of options but they were all pretty expensive. Then I came across a local company that sells used food grade liquid totes. These are the 275 gallon variety with the metal cage around them. I was able to check some of these out. Although the plastic is not so stout (they are meant to hold liquid in, not any external pressure) with the metal cage I thought they would do what I needed. I bought four of them so I would have a storage capacity of about 1,100 gallons. These totes are about a 4 foot cube. I used a mini excavator to dig the hole. I made it 16 feet long, 5 feet wide and 4 feet deep. If I had it to do over again I would make the hole 6 feet wide to allow better access to connect the totes to each other. Once the hole was dug, I began to place the totes in it. I first placed two totes and connected them to each other with PVC pipe, leaving a stub for the next. Then I placed the following two, connecting them to the others as I placed them. Once I had all the connections made, I placed concrete backer board all around the outside of the totes up against the metal frame and backfilled. This way the force of the earth – when backfilled – would be against the concrete backer board and the metal frames, not against the plastic sides of the totes. I then covered the tops of the totes with ¾ inch pressure treated plywood backed with 2x4s to hold the 8 inch or so layer of dirt that I put on top of the totes. I cut holes in the top of the plywood to allow access to the top caps of the two outermost totes. One is to allow the drainage system from my gutters to fill the totes. I routed all my gutters into drain pipe that comes to the where the totes are buried. I also built a small filter box to filter off any debris that comes through the gutters and grain pipes and then the filtered water flows into the totes. Any debris that makes it through the filter should will settle out in the first or second tote and not make it to the last tote – the other one with a hole in the plywood for access. This hole is to allow access to the water.  I currently have a well pump in the last tote to pump water out for irrigation. This could also be used to access the water to fill buckets via a hand pump or a variety of other methods. So far it has worked fine for me. Anyone wanting to try this may want to check local water law in their area. It is not legal to harvest rain water in this way in many states.
These totes are not meant to hold side loads, but they are meant to hold vertical loads. They are designed to be stacked two high. A tote, when full, weighs well over 2,000 lbs. So, to have a layer of dirt on top is no problem as long as the plywood can support it, the tote can too. With the metal frame and the backer board on the sides they should be fine for side loads too. Even if they had no frame, as long as they have water in them they would never collapse from the weight of the surrounding dirt. With the metal frame and backer board they will be fine for those periods when they are closer to empty. I hope to never run them completely dry, but if it does happen for a time I don’t worry about them being crushed by earth pressure because of the surrounding support provided by their own frames and the backer board to distribute the load onto the frame.
In any case, they are full today and I am enjoying having a large volume of water stored for any future need. Best Regards, – Tim P.

JWR Replies: Your clever idea just earned you a BFO Award, with an Amazon.com gift card to go along with it. Congrats!