Water Storage
The HR42 holds 185 gallons of fresh water in two large (connected) stainless tanks on the port side. In marinas with unknown water quality, we fill these tanks with dock-water, but we run it through a sediment filter and optionally, a Termix ceramic filter while filling the tanks. The tanks act as ballast for Whisper as well, and we need to manage the water in each tank manually with the valve between them (luckily, it's conveniently located). All house water gets routed through a carbon filter housing. We change this filter about once per quarter.
We initially estimated our daily consumption at somewhere between five and ten gallons a day, but have found that we actually consume between 15 and 25 gallons per day depending on our activities. Either way, we absolutely wanted a water making (desalination) capability to keep the tanks topped-up daily.
We sacrificed the cabinet in the forward head for the watermaker installation.
Watermaking
For making fresh water (desalinating seawater via a reverse osmosis membrane), we chose the Spectra Santa Cruz 380 watermaker. The Spectra is a 12V DC unit with two small 12V feed pumps and a large hydraulic "Clark pump". The Clark pump delivers high pressure brine/salt water to a reverse osmosis membrane. Pumping saltwater at high pressures through the membrane converts a small portion of the salt water to fresh (almost distilled quality) water.
With the extra feed pump, the unit is supposed to make about 15-18 gallons/hour. Best case, our unit only makes about 12-14 gallons an hour. Unfortunately, our normal daily water consumption in the tropics can be as high as 15-25 gallons/day. This might include rinsing dive gear, rinsing off after swims, dishes after two/three meals a day, a shower for each of us, a couple gallons of drinking water, a bit of laundry, and normal hand washing. Yes, "we use water like we make it". We probably needed a bigger two membrane genset engine driven watermaker that could replace our consumed water in less than an hour.
When we first installed the unit in the summer of 2001, we have had numerous issues. Once all of those issues were sorted out, the unit settled into a routine and usually worked -- at least on one pump. By 2004, we needed a major overhaul and we were quite frustrated with the unit. We fixed it in Tahiti and had good luck with it until we reached New Zealand. We then pickled it and left it sit for a couple of years. When un-pickled, we found two corroded and failed valves and failing pump heads (again), so in 2007 and 2008, we replaced the two automatic valves (backflush and rejection) and the two pump heads.
Spectra (manufacturer) has been fairly responsive over the years and has provided decent service. We received replacement parts — a new membrane, Clark pump, and two new Shurflo pump heads in 2003 and 2004. We did not have to pay for the Clark Pump or the pump heads (because they were still under warranty). We purchased the new membrane, and also learned that we shouldn't expect more than a few years on a membrane on this model of Spectra. The flow of water is too low for the amount of fresh water extracted, which shortens the life of the membrane.
As of March 2008, the 380 is chugging along on one pump right now, making about 6 gallons per hour while waiting for Duncan to install the new pump heads. The Spectra service company here in Auckland (Albany) — Enertec Services — has been very responsive with parts and support. Spectra no longer makes this model, so no need for our review of it's performance. We hope newer models are a bit more reliable and the specifications are met in actual use. Also, we would probably go the easy-access "component" route next time on a water making system, rather than everything mounted permanently behind a pretty control panel. The control panel is very tedious to remove to get access to pumps and valves and makes it very difficult to perform the frequently required maintenance. Mind you, we like the control panel, just not hiding all the pumps, filter housings, and valves behind it.
The same cabinet with the doors open. We wanted to preserve a small shelf above the unit. This was a mistake -- we should have mounted it as high as possible to make filter changing easier. The small slot at the bottom is how I access the filter(s).
The new 10 micron pre-filter and seawater strainer are much easier to reach -- mounted in a cabinet below the sink (and waterline).
Water Heating
For water heating, we have a 11 gallon 800W 120V AC water heater, that also has a thermal heat-exchanger loop inside. This loop is now integrated with new DCGen generator. Every time the genset runs (daily when away from the dock) it heats the water in the water heater. The tank is insulated well, so a full hot water tank is usually good for one day worth of showers and dishes. In a marina, we rely on the 800W 120V AC heating element for water heating. We just "plug-in" to get hot water. When in 240V/50Hz countries, our 2500W TSL step-down (to 120V) transformer is sufficient to handle both the max 100 amps (1000W) of battery charging and 800W of water heating.
Duncan designed a fancy dual-source, single heat-loop "switching manifold" that would allow us to heat water from either the engine or the genset, and even considered adding another loop to our existing hot water heater, but the high cost (over $500 US) of implementing one of these options left us feeling the 80% solution — just heating water using the genset — was more than sufficient.