The system comes with a T valve for the water pickup, so that the input can be sourced from either the thru-hull or from a container in which you have mixed the bicide solution (the only cleaning you should have to do more than very occasionally). It comes with another T that lets you choose to send the product water either to the overboard drain (connected into the sink drain line) or to the FW tank. I put a third T valve in the product water output line, before it gets to the drain/FW tank choice valve, that allows me to pull off a few ounces of water to test it for quality before I start sending it toward the FW tank.
I give the watermaker 10 minutes to get fired up and pack enough salt into the membrance so that it can actually work, while product water heads for the drain. Then I turn the first T to get a sample, turn the T back, and test the sample. If it passes, I turn the second T to allow product water to go to the FW tank. The line delivering the sample to your test cup has to be pretty short, unless you want to wait a while to be sure what you're sampling is indeed freshly produced product water.
It's pretty easy to distinguish perfectly clean product water from unsatisfactory water. Two varieties of unsat water:
1) too salty - maybe the membrane needs cleaning or replacing (we've replaced ours once, about 5 years ago), and
2) smells of decomposing sea creatures, usually because the primary intake filter hasn't been cleaned recently enough (needs it once a week or soin the PNW) and is looking a bit green. #2 is much more common.
Cleaning the primary filter is simple - unscrew the large cylindrical filter's clear plastic case, and blast filter and case with clean seawater via a washdown pump. If you do this regularly the filter element will last all summer.
As long as you make sure never to take in dirty water (such as in a harbor - petroleum is very bad for the membrane), and keep everything clean by cleaning the primary filter regularly and biociding the system if you're going to let it sit unused for several days, it should stay working for a long time.
This is the smallest, but most manually-operated of powered watermakers. My friends who have a little more room installed an 8 gal/hour watermaker that did some back flushing automagically.