Optimizing Freshwater Flush - Shurflo Pump Systems


Note: Shurflo systems include Ventura, Cape Horn, 180/200/380c, Gulfstream, & Santa Cruz Models:


Optimizing the Fresh Water Flush Duration Overview:

5 minutes or so is usually the right flush duration to ensure that sea water is thoroughly flushed out of the watermaker using the least amount of fresh water. However, due to different lengths of hose runs, different rates of flow, and different pressures in shipboard fresh water systems, the flush duration can be optimized for your boat: Your system may require more than 5 minutes to adequately flush the system, or you might need less time, allowing you to save more fresh water. However, you must ensure the system is adequately flushed. Do not try to save a gallon of water at the expense of your system longevity, run your watermaker for a few more minutes to make up the difference.

Optimize the time:

Ideally the salinity of the brine discharge will be completely fresh just as the flush cycle is completed. Using the brine discharge service hose, direct the brine discharge into a bucket. While the system is freshwater flushing, take repeated samples from the brine discharge and test it with a handheld salinity meter. When the PPM drops below 1000 you can consider the system to have been fresh water flushed and note the elapsed time. This will be your optimum flush duration going forward.


If there is salt in the water, flush for another 5 minutes and test again. If there is still salt in the water, it is most likely being drawn in from the ocean. If this is the case you will have to close your thru hull or similar valve before you flush to ensure you don’t get any seawater contamination (on MPC systems you can increase the pump off time to push more water upstream).