Connecting 2 Reservoirs or Tanks: A Simple DIY Method

Connecting 2 Reservoirs or Tanks: A Simple DIY Method

We recently added more rails to our indoor hydroponic system and with it we needed to add more reservoir capacity. We had one 27-gallon reservoir serving two 4-rail systems. It worked, but required the nutrient solution to be topped off quite often. One option was to simply buy a bigger reservoir and use that, but we decided against it for two reasons. First, we don't have a lot of extra space to begin with, so we didn't want an even bigger tote taking up space. Second, and most importantly, our lower hydroponic system drains back into the reservoir by gravity, and therefore must be above the top of the reservoir. If we had a reservoir any taller than the 27-gallon tote we currently use, the lower system would no longer be able to drain.

Another option was to add a second reservoir and build a connection between the two. This would allow me to hide the second reservoir underneath the rails and keep both reservoirs below our lower hydroponic system to still allow it to drain. My concern was that a connection could be complex or be susceptible to leaks so I set out to find a solution that would be robust but simple and cost-effective.

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  • (2) 1" PVC Male Conduit Fitting (Home Depot)
  • (2) 1" PVC Female Conduit Fitting (Home Depot)
  • (2) 1" PVC Ball Valve Slip x Slip (Home Depot)
  • (1) 1" PVC Union (Home Depot)
  • (2) #45 O-Ring (1-3/8" OD x 1-3/16" ID x 3/32" Wall) (Menards)
  • (1) 1" PVC Pipe (to connect each piece) (Home Depot)

Between the tanks, I decided to use two 1" ball valves and a PVC union. The ball valves allow me to close the connection to either reservoir and the PVC union would allow for the reservoirs to be separated for maintenance or moving. They are then connected by a short piece of 1" PVC pipe and PVC glue. This is similar to the design I use for connecting the rails in our hydroponic system - it's a simple, leak-free design that allows for quick disconnect.

For attaching to the tank walls, I used an unlikely combination - PVC conduit adapters. Bulkhead fittings could also work, but they are much more expensive and more complex. PVC conduit fittings are super cheap and can be glued to a PVC pipe with regular PVC glue. I used conduit fittings instead of regular PVC fittings because conduit fittings do not have tapered threads so they can be tightened together to form a pinch on the tank wall. PVC fittings with NPT threads will intentionally bind as they are tightened, so they will not work for this application.

Before attaching to the tank wall, I connected the male conduit adapter fitting to the ball valve using another short section of 1" PVC pipe and PVC glue. Then I drilled a 1.25" diameter hole near the base of each tank. The threaded portion of the male conduit fitting just barely fits through the 1.25" hole. Before inserting the male conduit fitting through the hole, I added a #45 O-ring to seal up any gaps once the fittings are tightened. It's important that the O-ring is placed on the same side of the tank wall as the male conduit fitting - this stops leaks from traveling up through the threads and out of the tank. The male conduit fitting was then inserted through the 1.25" hole from the outside, with the female fitting threaded on from the inside of the tank and tightened to form a seal. Doing this on both sides leads to a leak-free and isolatable connection!

Inside of tank wall showing female conduit fitting Both sides of tank wall

This setup allows for nutrient solution to be added to one reservoir without accessing the other - any water that is added to one reservoir automatically balances out with the other. I would recommend putting the pumps into one reservoir and the drain tubes in the other - this ensures that water is circulating between the reservoirs.

I utilized this solution for a hydroponic system but I'm sure it would work for other applications as well - rain barrels, watering tanks, etc. For situations when isolation is not required, you could remove the ball valves and union and this would be about as simple as you can get. Hope you find this helpful!