There are some other things you need to consider when looking for a watermaker.
What power source are you going to use to power the pressure pump? There are few different designs available including 120V, 12/24V, hydraulic, and even positive displacement
piston pumps that run off of a PTO from a generator
, or even off of the boats main engine
I prefer to power off of the main engine
as it allows me to use larger membranes and make more water
(1.5-2.0 GPM) without worrying about the amps. The low voltage DC pumps are only used with the smaller production systems and I have found them not to be as reliable as the 120V systems. Dont get me wrong, the 12/24V RO systems work ok, but the pumps dont last or perform like the 120V, or the PTO style pumps.
One misconception is that there are "low maintenance" watermakers, and I will tell you that ALL RO systems require maintenance
and how you take care of it will directly reflect the water quality, water quanity, and life of your watermaker.
I read a post from a gentlemen that only uses his watermaker when he is in crystal clear water. This is a great rule
of thumb unless you want to invest in a SDI (silt density index) test kit to insure you are not "fouling" your systems membrane (RO filter) with poor quality feed water. The pre-filter on the systems only filter down to 5 or 1 microns while the RO membrane filters down to below 0.001 microns. Water containing a lot of particles lower than 5 or 1 microns can easily plug
or foul the membrane. It is most important that you check your pre-filter at least monthly on a liveaboard
and change it when the inside center core
of the filter shows ANY discoloration.
Next is RO membrane care. It is so easy to set your watermaker up to flush itself with purified water that I can not understand why every watermaker owner doesnt do it. This little thing can extend your membranes life by two or three years over those that dont. Some systems have this feature built in, but it is costly, and setting it up consists of two simple valves, and five minutes of your time after filling your tanks
Concentrate / Reject flow (system discharge water) needs to be checked regularly as well. The heart of your watermaker is the RO membrane, and it is basicly an artificial kidney. It needs to discharge 2.5 - 3 gallons for every gallon of water produced. Improper discharge rates will kill a system faster than any other thing and if equiped with an orifice valve to control this function remember that the orifice can become plugged and needs to be checked and cleaned regularly.
When choosing a watermaker, I always recommend that the simple systems make the best systems. Make sure that your system has a TDS (total desolved solids) monitor
, concentrate flow meter, permeate ( purified water) flow meter, and a low water pressure system shut down. The rest of the bells and whistles on them are meaningless.
Hope this helps, and feel free to ask me anything regarding water treatment systems.