Originally Posted by HeadMistress
Installing the loop isn't that bad a job, actually, if you put it immediately after the toilet...just switch out to a 90 discharge fitting if you don't already have one, rotate it to aim it up...mount the loop on the bulkhead behind the toilet and come down to connect with the rest of the discharge line. And you'll find the loop has an unexpected advantage: you'll only have to flush long enough to clear the top of the loop...gravity will take it the rest of the way to the tank. Switch to dry bowl (assuming that your toilet has that capabilty) to push some rinse water over the top and you'll reduce any run back to less than half a cup. Or don't...instead remove the joker valve and you'll have a bowl that can hold water "like the one at home."
Yes, easy job if you're OK with the loop and hoses in plain sight. If you want the loop out of sight (under an adjacent vanity, for example) it's typically a major pain in the neck...but it can be done.
Gravity will only take all of the sewage flow from the loop to the tank if the line after the loop is down hill all the way. Some will still pool in an uphill discharge hose if you "come down to connect with the rest of the discharge line" (presumably at the original level of the pump discharge). But at least it wouldn't back into the bowl. I'd attempt to use the height advantage to reroute a rigid line directly to the exit from the loop.
Any water, clean or otherwise, that is in the column between the exit from the pump and the top of the loop will drain back when the pump stops. I'm not familiar with a dry flush feature, but don't believe it would preclude drain back into the bowl resulting from a loop installation. In my experience, joker valves invariably leak...so you'll have water in the bowl whether the valve is there or not. Take it out and the pumping action also improves. The installations in our boat (~24" of hose from the pump exit to the top of the loop...both located under adjacent vanities) result in a 5" diameter pool of water in the bowl of the old Raritan Crown. Never had a splash issue underway. I mounted the loop as high as possible (under the vanities) to achieve a constant gradient to the tank.
For our forward head I relocated the Y valve such that it sits directly under the exit from the loop. Super tight installation under the vanity counter top and next to the sink. But completely out of sight. Have to remove the drawer next to the sink to access the Y valve. The pollution police don't have a clue how it all works or even that it's there..