Sippin’ on seawater

Before the advent of watermakers, boats would set to sea with as much water as they could hold, tanks full to the brim and jerry jugs lining the lifelines. Rainwater was funneled into tanks for drinking or used for other tasks (e.g., laundry, bathing), a practice that continues among cruisers today. Many, but not all, modern-day cruising boats are equipped with watermakers, and we are fortunate to have one.

Watermakers transform sea water into potable drinking water via reverse osmosis (i.e., magic!). Water is siphoned from the sea and forced through a series of filters (i.e., charcoal ⇒ 50 micron ⇒ 20 micron ⇒ 5 micron) to remove impurities. In addition to replenishing our water supply when we receive insufficient rainfall or consume gluttonous amounts during passages (we’ll try to resist the latter), having a watermaker will help to protect us from waterborne illnesses in regions where water quality is poor. We’ll simply make our own!

The Red Thread is equipped with a Spectra Catalina 300 Deluxe that was installed by the prior owners. She had been pickled (i.e., winterized with propylene glycol) for longer than is recommended (ahem, since we purchased her in 2012), and we were worried that we may have destroyed an important and expensive piece of equipment. Fortunately, when we unpickled her with the aid of our good friend, Glenn, The Red Thread’s prior owner, we found that was not the case. Whew! After some routine maintenance (e.g., replaced hoses, changed filters), our Spectra started right up! Over the past month or so, we’ve routinely flushed the system every few days to keep it in working condition. However, until a few days ago, we had not tested the water to make sure it was safe to drink. Needless to say, we hadn’t put any in our tanks…

Water quality is measured using a device called a total dissolved solids (TDS) meter. TDS is the term used to describe the amount of mobile charged ions (e.g., salts, minerals, metals) that are present in a volume of water. TDS are represented in parts per million (PPM). The lower the TDS score, the better (see below).

Our watermaker is mounted in the transom of our boat, and there is a small hose that allows us to produce a test stream. Last weekend, we pulled on our headlamps, crawled into the transom, and got down to business. We started by testing our tap water, which comes from the Elliott Bay Marina’s city water supply. We then conducted serial tests of our watermaker water in five-minute increments. Testing the water is simple. We turn on our HM Digital COM-100 TDS meter, and swirl it in a sample for about 30 seconds. Our results in ppm were as follows:

Tap water:  32.5IMG_0486_edit
Minute 0:    38.0
Minute 5:    30.8
Minute 10:   30.2

WOOT WOOT! I’m happy to report that we have good news on the water quality front and one more “to-do” crossed off our behemoth pre-cruising list! Our tap water is of excellent quality and our watermaker water is even better! SCORE! Even though our watermaker is capable of producing excellent water, the thought of filling our tanks with marina juice creeps us both out a little bit. After all, Neil knows what’s down there from his zinc-changing scuba expeditions, and it’s not pretty! We’ll be holding off on filling our tanks until we’re out in the open water of the Puget Sound.

7 thoughts on “Sippin’ on seawater

  1. You are too cute! Love your pic and love how nerdy this little post is- my science geeks at school would love it! 🙂 Love you guys!


    • HA! Thanks, Suz!! You know Neil and I are both pretty nerdy at heart…the computer geek and the scientist ❤ By all means, feel free to share our blog with your students, if you think they'd be interested in following our adventure!


    • Glad you found this post useful! If you couldn’t tell, I was oddly giddy about the watermaking process and the grand discovery that our homemade H2O is awesome 🙂 I feel very grateful that our boat had one when we bought it — it will make a big difference in our ability to be self-sufficient out there. ~Jessie


  2. Pingback: Ready, set, sail: San Juan Islands shakedown | s/v The Red Thread

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