Herk, I resemble that Navy water remark.
I used to make the fresh water on my first ship, ran two 12,000 gallon per day 2 stage flash type distilling units. Located in the engine room, 110-120* working there most times when operating down near the Equator. Fresh water is down right precious on a small ship. Boilers take first priority then the crew. No water for boiler, no steam. No steam, ship does not move, bad ju-ju... First deployment we had one distilling unit break down, went on "water hours". Crew could wash hands, brush teeth, and shave. No showers for about a week before we got things fixed. We were quite fragrant... Then after things were fixed we at first had a Master At Arms standing by the shower with a watch, you had a total of 90 seconds of running water, no more. THAT was a Navy shower.
To the original post, depending on where your shower is located the factory may have plumbed the shower to the galley tank instead of the grey tank. They probably did this because the shower is on one side of the unit and the grey tank is way the hey over on the other side. My Sunseeker is set up this way. We shower at the campground facilities and keep an eye on the "notional" galley tank level on the indicator panel, hit 2/3 and dump. No worries, mon.
Chris in Virginia
2006 Sunseeker 3100SS/LTD
2008 Smart Passion Cabriolet TOAD
1986 Honda Helix (Original owner)