Ideal fresh water flush duration for Spectra 300 water maker

[LifesBetterWhenYoureBeating]

My Catalina 300 was configured to run the fresh water flush for 5 minutes, but I've measured the brine discharge and it amounted to 5 gallons during that time. Then I saw the following comment by a Spectra specialist on
https://www.cruisersforum.com/forums...ml#post1728603

Timing your fresh water flush time by a standard 2.5 minutes doesn't always work and neither does watching for the pressure drop on either manual units like yours or fully automated systems. For you it's a simple thing to figure out. Break out your brine discharge pickling hose and attach it to the Clark pump. Route the hose into a five gallon bucket. Start the system and time how long it takes to fill 2.5-3 gallons of water into the five gallon bucket. This is now the real time you flush your system for

I'm wondering if 2.5-3 gallons would be enough to completely flush my system as well?

[ItDepends]

A good rule of thumb is to flush any system with 3X the internal volume. The number of 2.5 to 3 gallons seems really close to that number, for that model watermaker, so would should be good. Of course, extra flushing is not bad, it just uses a bit extra water.

Flushing 2 gallons of water more than "required" means you run the water maker for an extra 5 minutes. Only you can decide if it is worth sharpening your pencil that much.

[Tellie]

Let me further explain to avoid any confusion, with a bit of context in an answer I was giving someone else. There is only one way to ensure your watermaker is "Properly" fresh water flushed (FWF) and this means every watermaker made that freshwater flushes. When you measure the brine discharge on your system for a proper flush, you are not measuring the volume run through the system but rather the PPMs of the brine water when the flush is done. You need to have the brine discharge down to 1,000PPMs or below, preferably below. You can only do this with a handheld TDS meter. Run your system for a few minutes to saturate it with salt water. Then flush your system for three minutes and stop your system. Break open the brine quick disconnect and measure the water that comes out here with the meter. If it is higher than 1,000PPMs run your freshwater flush for another minute and stop again(4 total) then re-test the brine discharge. If it is still higher but coming down run another minute until you get it below 1,000PPMs Once you are below 1,000 PPMs, that is the amount of time you set to flush your system. This may be 6 minutes it may be 3 minutes. Every boat and watermaker will be different because of installation variances and house freshwater pump capacities. This is "THEE" single one thing that dooms watermakers because the FWF was never set up properly from the beginning. Adjustments might need to be made on feed pumps to make this work as well. A feed pump that is demanding more water than your house pressure pump can deliver will never properly FWF your watermaker regardless of how many gallons of fresh water you run through it. Consistently draw in a slight amount of salt water through the intake thru hull because your house pump can't keep up with the feed pump demand and you can drain your tanks or flush 10,000 gallons of fresh water through your watermaker and it still won't be properly flushed and the membrane will suffer sooner than later. Every time I hear, "My product water smells bad every time I start my system" or " My product water shows high TDS readings on startup but eventually comes down in a few minutes" it's 99% of the time a FWF system that is not set up properly. This is a personal aggravation for me because I see so many so called watermaker experts out there that have zero idea about the FWF setup. I hear about the greatest and latest from these salesmen, but I see zero field experience in their comments. Next time you shop around for a watermaker, ask the salesman how many watermakers he has sold, and how many has he ever installed and serviced. I see a lot of engineering talk bantered about, but very little real field experience.