Originally Posted by wolfenzee
This thread has lead me to talk to a number of sailors who have actually done extensive cruising (including circum nav)....all of them (and other people they have run across in their travels) function quite comfortably with small water makers. Including cooking
, showering, drinking, etc average around 3 gpd/person (some allowed 5 but ended up using 3). If you listen to the salesman at the boatshow you will be debating between a 20gph or 30gph watermaker. Watermaters don't have to be tended, with a low draw watermaker and solar or wind generator
, you can just let it run (PUR makes a sound proof enclosure...of course so could you). There was one called the "Water log", a propeller
dragged behind the boat and powered the pump (like an old fashion knot
log). There is no reason to spend alot more money
to be able to get it done faster, your not in a hurry...where are you going.
We run in different circles - I have yet to meet a cruiser with a low output watermaker that did not want a higher output one. And these are also cruisers with extensive experience and circumnavigations.
I know 3 cruisers with the PUR40, which fits your definition of low amp, low output. All three of them are getting rid of it because the concept
of low amp, low output just doesn't work in practice. 4 amps drawn continuously for half a day is a lot of current
for not much water from a 1-2 gph machine. And getting oneself out of a low water "hole" is excruciating.
And while we are on the subject of salesman, the real crime is making you believe output. Be aware that all stated output specs are for 72*F water temp, brand new membrane and 13.8V at the pump terminals themselves. As your conditions deviate from these, the output drops quite a bit. The power is the biggie - if you plan to run off solar, there is little chance you will be at 13.8V terminal voltage on the machine. Count on 15-20% less when running at a terminal voltage below 12.7V.
So assuming 12.7V (a good assumption when running under solar), water temps out of spec and a not new membrane, you will be getting ~1.3 gph out of a PUR40 type machine. You will be able to run it for ~6 hours at that rate using solar (you will need 85W of solar just to run it alone) and it will cost you 20-30A of battery
. This is not a good return or conservative use of your power.
But the point you are really missing here is that the 20-30gpd watermakers are the same price
as, or less than, most 5-8 gal/day ones. And that is leaving Spectra off the table completely. This has been pointed out to you several times on this thread, but you still debate about how much money they cost just for more water faster.
Your arguments for upfront and maintenance
costs are specious. Have you actually priced (for instance) a 20gph CruiserRO system and a 6gph Village Marine
Little Wonder? Then go and price the 8gph Spectra if you want a shock. Any money you save on your PUR40 is going to be spent again over time in terms of membrane replacements
and spare parts
kits (price them - you will be stunned - your first membrane replacement is going to cost you ~$500 more than one for a 20gph system). The 20gph HP pump can be rebuilt almost anywhere in the world by any common pump repair place. Your PUR pump will cost ~$800 to be fixed/replaced if it goes down.
When you get to the tropics, where the sun is blistering hot, the water is warm and sticky, you have both recreational gear
and boat gear
that requires fresh water rinsing, there is no rain for 4-6 months at a time, and the wind
from the breaking reef waves on your boat constantly, you will want more fresh water than 3 gallons per day. I drink 1-2 gallons of water each day just staying hydrated. The salt
is insidious when the trades have the water vapor whipped in the air - I need to clean my eyeglasses 2-3 times each afternoon just reading in the cockpit because of the film of salt that accumulates on them. The boat is encrusted and the decks slippery.
You are also assuming that people with 20-30gpd units are using 20-30gpd. Going on about how wasteful and environmentally harmful these people are blinds you to the reality that one is often times in areas where one does not want to make water. And when one does want to make water, it is far better to make a lot of it at once to make most efficient use of the feed water quality, the power available, etc.
Can one cruise
on 3gpd? Absolutely. We use ~4-5gal/day each and laundry
takes a big bite every couple of weeks. But right now, our boat is covered in salt and dirt and we would like to do laundry
a bit more often. Our unit runs for "free" off our solar, but doesn't leave much for recharging the batteries so we need to balance it with generator
time. We will be replacing our running 6gph unit with a 20gph one in the near future. If we run the generator
anyway, we may as well make a lot of water in shorter time.
The WaterLog system never worked. I have never seen a reported case of it working, and have read many reports of it not working. Even if it did work, the output was something like a gallon every 5 hrs or so.