Chemical Metering Pumps

Sodium Hypochlorite has an extreme tendency to off gas which can cause a metering pump to vapor lock, seize up, or even lose prime. Here are some suggestions to minimize the possibility of this happening.
  1. For metering applications where the feed rate is less than 2 GPH, try using a pump with a self-deaerating head like the Alldos M205 listed on this website. These low flow rates allow more time for the Hypochlorite to off-gas and accumulate in the pump head. The self -deaerating design has an internal pressure relief and bleed valve allowing the gas to be vented safely backed into the day tank.

    Larger metering pumps will not be as susceptable to this type of failure, but I have listed several installation suggestions below that should be followed for all metering pump applications for Sodium Hypochlorite.

  2. Keep the suction line of the pump as short as possible. Pumps by their very nature pump better than they pull, so this is a good suggestion regardless of the liquid pumped. However, in this case, the shorter the suction line, the less the offgassing.

  3. Keep the feed tank out of direct sunlight, and avoid elevated temperatures. These conditions will increase the off-gassing of the liquid.

  4. Always use pressure relief, and bleed valves in your piping configuration.