Many of the well water treatment systems we offer at WaterFiltersOfAmerica.com® are dependent on the flow rate of the water past the pressure tank. While it is possible to estimate this flow rate based on variables like the pipe diameter and pressure tank pressure, we recommend a method that tends to give very accurate results:
- Locate a tap or faucet within earshot of the pressure tank and turn the cold water all the way on.
- Wait until you hear the pressure tank turn on and, with a timing device in hand, turn the water all the way off.
- Count how many seconds it takes until you hear that pressure tank turn off again and make note of this time.
- Without running the water again beforehand, take a container of easily measured size (i.e. a 5 gallon bucket or 1 gallon jug) and count how many gallons of cold water you can draw from that tap or faucet before the pressure tank again turns on.
In doing this, you can determine the water regeneration time of the pressure tank as well as the water capacity able to be drawn from that tank. If you take this data you can extrapolate to gallons per minute using the following formula:
Flow Rate = Water Drawn X 60
Flow rate is especially important for backwashing filters for two reasons. If the flow rate is too low there may not be enough water pressure to lift the bed of media during backwash, which can in time damage the media. On the other end of the spectrum, too high of a flow rate can cause excessive media washout during backwash. While we do have guidelines in place for recommendations and proper sizing of equipment, there are a lot of factors at play in determining which size unit to go with a particular flow rate.
Another area of treatment in which flow rate plays an important role is the treatment of E. Coli or Coliform bacteria. When using an ultraviolet light to sterilize the water it’s crucial to make sure that your UV light is sized to match your flow rate, though in this instance over-sizing the unit isn’t of as much concern as under-sizing the unit. If the unit is under-sized the bacteria won’t be exposed to the UV light for a long enough time to be neutralized, leading to potentially harmful bacteria getting into your water. For this same reason, when using chlorination and retention, it’s important to have at least 20 gallons of retention capacity for every gallon per minute of flow rate to ensure that the bacteria is in contact with chlorinated water for at least 20 minutes. Because there can be other factors in play when choosing or sizing a unit, we highly suggest calling one of our experienced water technicians at 1-800-684-0979 if there’s any uncertainty whatsoever as to what the best solution for you is.
-Water Filtration Wizard