Just wondering how long does one fill of water last on IP420 when cruising? Actually, let's rephrase it... What's your water tank capacity (any IP model) and how long does one filled water last with X amount of people on board?
We have been cruising about 4-5 months a year for the last 11 years. I asked the water consumption question to lots of other cruisers. From their answers, I would estimate that the average usage is 12-16 gallons per day for a cruising couple, ( i.e. 6-8 gals/person/day) for those with a water maker. It drops to 10-15 for those without a water maker. My wife and I use between 12-14 gallons / day, - living on board, showering in fresh water daily, cooking on board, using and washing real dishes. Occasionally washing out the cockpit with fresh water. We are careful but not crazy. No salt water bathing, no saltwater dish washing, not showering with a pump-up bug spray bottle, etc. We flush the toilets with sea water.
Some other opinions/observations:
1. Water makers make people less frugal with their water usage.
2. We have met cruisers w/o water makers that claim to be using 5-10 gallons per day with two people aboard, sometimes they smell.
3. As you get below 8 gallons per day for a couple I believe that you are approaching a back packing level of water use.
4. I think the UN standard to stay alive is a little less than two liters per day per person, so I guess this is the minimum.
5. Dogs and kids require more water, they are both fun but messier.
6. Boat guests can really change the usage - DON'T LET THEM WASH THE DISHES. They can dry them.
We carry 190 gallons on our IP 40, My strategy is to keep the tank between 3/4 and full, so if the water maker dies we will have at least 100 gallons. This is a very comfortable 7 day margin to either repair the water maker or find another water source.
Remember, when you make your water usage plan include a margin to accommodate over usage, AND the chance that your planned water refill port, may not have any water available for you when you get there, and you may have to sail to an alternative location.
Kind of a long answer, but I hope it gives you some more ideas to think about.
We have an IP 35 with 90 gallons, we have cruised her for months since 2002, and for the past 6 winters 6 months in the Bahamas. This past year we added a Spectra Ventura 200t which makes 8 gallons per hour at 8 amps 12 volt power, we run it on wind and solar.
As for water usage, my wife and I use fresh water to flush the toilet using the shower hose. We also shower every day at the end of the day by using a solar shower which is 5 gallons. This will work for two. We cook and do dishes with fresh water. We have found that on the conservative side we could get our usage down to 10 gallons a day with these jobs. We even will wash off the salt on the deck after a sail with fresh, 2-3 gallons.
For 10 years, I used flexible water jugs and I have hauled water via the dinghy every day 10 gallons or 20 every two days. This was getting old after all these years, so we installed the Spectra. Our goal was to run our entire boat off od 12 volt so this unit fits that goal well. We have 400 watts of solar and 450 watts of wind. In the Bahamas and Caribbean, we could run the water maker every day for one to two hours and we never had an issue with water,. Our tank was never below a half, and with our usage of 10 gallons a day and running the 8 gph water maker 1-2 hrs a day, we were always ahead.
I will say the spectra is expensive, it was $6,100 in Dec 2016, and I installed it myself on a mooring ball. It was really easy to install, took 3 days. This has changed up our cruising so much, We are totally independent now with water and power. This really changed up everything.
I will agree with George, that some boaters do not shower enough and this is noticable. Not an option for us, we like to use our solar shower right as soon as the sun goes down and then we are clean for cocktails and for dinner and the night. This has worked well and we can easily do this with 10 gallons a day, we have since 2002.