I was replacing the hose on my guest head, fortunately the easiest to reach of the three on board. Even so I was surprised by how difficult it was to work on and how long it took. I was able to purchase Shields white sanitary hose, looked just like what I was removing. This is smooth on the inside (important!) but has ridges on the outside. The ridges prevent the hose from moving smoothly because they catch on every edge. The bulkhead between the head and the ER is about 2 in thick because of sound insulation, so has to go in straight. Once in the ER the hose has to make a 90* bend just above the shaft. To make this bend the entire length has to be pulled through the bulkhead and then redirected. With one person pulling from the ER door and me pushing we could move about 3 in per push. By now I was lubricating the hose with olive oil to help it slip. My hose felt fairly new, but it had taken a set from being on the roll, so it would naturally veer off in one direction, and wanted to coil up again at each end. It was much like wrestling an anaconda in the tight confines of the guest head. See attack of the heat gun below.
Once I got started on this dirty task I did not want to stop until it was finished. It required lying in strange positions on dirty decks and using muscles I did not know I had. I would also try to do it back in the good old USA where parts are available if I broke or needed something. And parts are cheaper. I was lucky to have a boatyard nearby. So next time I would look at whether PVC pipe could be used for part of the run. Several pieces could be joined using the glued fittings without obstructing the inside. Its rigidity and smooth exterior would be easier to push through under decks. I did not want to cut my hose because the junctions and hose clamps would become future problem points. Wouldn't work in this case, but might for my other heads. Perhaps if I had had a bit more time (Admiral was "strongly encouraging" me to fix this immediately, was NOT pleased by my mention of the two other heads availability!!!) I would try uncoiling the Shields hose and weighting it down, leaving it in the hot sunshine for a day or so to see if it would relax a bit. This warmth would make it easier to bend as well. Trying to use the heat gun was daunting because the metal parts get really hot and there is no place to park it between uses. The only place for it to fall was on me.
In reference to the calcium deposits in the hose: I have read suggestions to pour vinegar or dilute hydrochloric acid into the toilet bowls to dissolve these deposits. I did this often, although not on a scheduled basis. Groco also recommends a little vegetable oil after this to lubricate the toilet parts. I haven't done this because of my LectraSan units downstream, but maybe I should. These probably benefit from lubrication too. Lastly I pumped a whole gallon of Raritan's new hose cleaner, C. H., through my heads, but too soon to know if it helped. All of my hoses were replaced 19 years ago. I did need to work on the hoses for our master head earlier in the trip, the one that gets the most use. These hoses looked fine. Of course the Admiral and I know to use lots of seawater when flushing. Perhaps I need to emphasize this a bit more for our guests.
Good luck. As I was walking through the small town of Man 'O war Cay with the coil of 15 ft of white hose wrapped around my shoulder, a voice emanated from the depths of the boat yard, "Well, that looks like a shitty job." That pretty well summed it up, and I hadn't even started yet.
I regret that this adventure seems to be my primary memory of an otherwise satisfactory cruise.
P.S. In looking up the name of Raritan's C.H. hose cleaner a moment ago I noticed their Saniflex marine hose. It doesn't appear to have the exterior ridges that Shields hose does. Worth a look.
www.raritaneng.com
