I often get asked if a simple water storage tank like a rain barrel, can be used to provide water for a misting system. In this day and age, many folks are thinking greener and using barrels or drums to collect water from their downspouts when it rains. Can this water be used for a misting system? The answer is simple; yes and no.
Why you cannot use a water storage tank for misting-gallons required:
The problem with using a storage tank for misting is not that it will not provide enough water nor enough water pressure to satisfy your misting system. First, I will demonstrate the volume of water needed, then the water pressure a misting system requires. We will use a Dramm pin perfect nozzle with a green pin as an example.
A Dramm pin perfect nozzle that uses the green pin uses .69 gallons per minute at 15psi, .82 at 22psi, .95 at 29psi, and 1.08 at 36psi. To make that a bit clearer, if the water pressure is just 15psi, the misting nozzle will use .69 gallons of water if run continuously for 1 minute. Assuming you have a 55 gallon water storage tank, you could get about 80 minutes of continuous flow if using 1 pin perfect misting nozzle. (55 gallons divided by .69 gallons per minute =79.7 minutes). Assuming you are misting for 10 seconds every minute you would be misting only 72 minutes out of a 12 hour day and using 49.68 gallons of water. (12 hours times 60 (minutes) = 720 minutes. 720 divided by 10 (seconds of mist every minute) = 72 minutes of mist in a 12 hour day. 72 times .69 (gallons per minute) = 49.68 gallons of water is needed). Remember, this is using just ONE misting nozzle! If you are using more than one, the number of gallons used in a 12 hour period will be even more. The number of minutes you could mist per day will be reduced also.
This example is assuming your water pressure is only 15psi. Most misting systems used for propagating plants will average 40psi or more. Remember, at 36psi, one Dramm pin perfect misting nozzle using the green pin uses 1.08 gallons per minute. This means that in the same 12 hour period, the single misting nozzle would use 77 gallons of water! (12 hours times 60 (minutes) = 720 minutes . 720 divided by 10 seconds of mist per minute = 72 minutes of mist per 12 hour period. 72 times 1.08 (gallons per minute) = 77 gallons of water needed.) Using the same 55 gallon barrel (and assuming you can get the 36psi pressure) the 55 gallon barrel would not supply enough water for just two misting nozzles for a single day! Using a much larger tank would provide the required amount of water (assuming you can fill it every day), but how will you provide enough water pressure?
Why you cannot use a water storage tank for misting-pressure required:
The example above mentions the average pressure a misting system for propagating plants requires. This pressure was 40 pounds per square inch, or 40psi. 1 psi is equal to a column of water 2.31 feet high (at sea level). This means that for your 55 gallon barrel (or any other tank for that matter) to provide just 1 psi, it would need to be raised 2.31 feet above sea level to provide that 1psi. To get 15psi, we would have to raise the container 34.65 feet (15 times 2.31 = 34.65). Remember, 1psi=2.31 feet which means that if we want 15 psi, we need to raise the container 15 times the 2.31 foot measurement. WOW, can you imagine raising a barrel or other container almost 35 feet into the air just to get 15 pounds of pressure to your misting system? Me neither! Without raising the water storage tank to unspeakable (and unsafe!) heights, the only alternative is using a pump to deliver the proper pressure. But remember, this is assuming your tank is large enough to provide the amount of water required for the number of misting nozzles you have.
My experience is that using a water storage tank to provide water to a misting system is wasted time and money unless you do the math to determine if your tank is high enough and large enough to provide the volume and pressures required. Even if you have a storage tank large enough to provide the required amount of water every day, there are a few questions you need to ask yourself, like:
- Do you have the time and resources to fill it every day?
- Do you have electricity nearby to power the pump that is required to provide enough pressure to supply your misting system?
- Can you use the time and money required to get the water storage tank to work for something better, like installing a water line from a well or city water?
Before committing to using a rainbarrel or other water storage container to provide water to your misting system, a bit of research beforehand will save you a ton of frustration later.