The distance isn't long enough for 1/2" diameter to make any noticeable difference in the velocity. The industry standard for toilet and tank discharge hoses have always been 1.5" Jabsco is the only exception...their toilet discharge hoses have always been 1", but even they began using discharge fittings that will accept either 1" or 1.5". Raritan began offering a discharge fitting that can take either one for just one reason: to accommodate buyers who are upgrading from Jabsco toilets but keeping their hoses.
As for sea water mineral buildup in the toilet discharge line...whether the line is 1" or 1.5" makes no difference. It can easily be prevented by a cupful of distilled white vinegar flushed all the way through to the tank, followed by a quart of clean fresh water once a month.
]I know in gravity lines one doesn't what to have too great a slope >1% as the water/liquids with pass the solids and leave them behind...
I don't know where you got that. It may apply to household toilets but not to marine toilets because, unlike household toilets, marine toilets have pumps that push the bowl contents--solids (which are broken up as they pass through the pump) and liquids together-- through the discharge line. There are many boats that have toilets above the waterline and tanks in the bilge--the slope can be anything from 10 degrees to vertical. On the typical sailboat that can have a tank with an inlet fitting higher than the toilet discharge fitting, I often recommend installing a loop--not necessarily a vented loop, just a loop--immediately after the toilet because the user only has to pump or leave his finger on the button long enough to push waste over the top of the loop, gravity gets it the rest of the way. This not only helps to prevent run back, but if the toilet is flushed in the dry mode, followed by only enough water to rinse behind the flush it can double the number of flushes a tank can hold. First, solids are broken up even in a manual toilet...second, bowl contents aren't just flowing downhill from a marine toilet, they're being pushed by the toilet pump. Velocity is impossible to
...but in the case of a macerater pumped line to the holding tank, would this hold true? as everything becomes a liquid(y) flow.
Macerated or unmacerated, it makes no difference
It would be good to know the ideal fluid velocity for a waste line
Impossible to calculate because there are so many variables-- for instance...The diameter of the piston in most manual toilets is 1.75"...the diameter of the piston in the Rarian PHII is 2.5". When you calculate the cubic inch capacity (displacement) of the PHII with a 2 1/2" diameter piston, it comes out to a little over 12 cubic inches. If you do the same calculation for a pump with a 1 3/4" diameter piston with the same stroke, the cubic inch capacity is only 6 cubic inches...which means the PHII can move twice as much per stroke as other manual toilets. There are also variables in the ability of electric pumps to move waste...A Jabsco macerator pump is rated to move waste through it @ 12 gallons/minute. The pumps in some high end all china "thrones" can move waste 30' in a few seconds...the Tecma Silence can move waste up to 90 linear METERS, 30 vertical METERS! And there's a lot more variation in both manual and electric toilets including how vigorously (or not) the user pumps and how well maintain his toilet is.
Why do I have the feeling that you've been trying to apply fluid dynamic "rules" to marine toilet systems...??
If so, I hope I've managed to explain why you can't.
--Peggie
