Peg,

I am curious about having a gravity feed toilet reduced from 3" down to 1.5" before the waste is macerated. Would this not cause a problem of solid waste getting stuck in the plumbing?

That thought also occured to me, which is why I emphasized "SHOULD" work and also early strongly recommended discussing it with Raritan before buying any of the equipment.

BUT...1.5" is only 1/2 smaller in diameter than the discharge of a household toilet....about half a bowl of water would be added ahead of any solids deposit, which SHOULD (again I stress that word) be enough for gravity to wash solids the way into the L/S.

If it won't work, adding an inline macerator pump is not the answer...it would create more problems than it would solve. Macerator pumps move 12 gal/minute, and gravity RV toilets are not electric, so there's no way to wire it to the flush pedal...which means it would be almost impossible to limit the running time short enough to only run while about a quart is going through it...and letting it run dry for longer would fry impeller in the macerator pump.

So either the L/S can be made to work with a gravity toilet by reducing the plumbing, or he's gonna have to choose another toilet...or go with a holding tank.

well I spoke with someone at Raritan , he said that it is a flow
through device, the head must have a pump, as the heads pump
does more than just getting the waste to the lectra/san, it also needs
the heads pump to get the waste out of the lectra/san and out the
sea/cock, the lectra/san has no internal pump whatsoever, doesn't
seem like a smart design.

thank you
Jason Miller

Nothing wrong with that design...in fact, it's smarter than most. The waste comes in near the bottom of the first chamber and overflows out the top of the second chamber....thus making sure that the amount discharged is only equal to the amount coming into it, which reduces the odds of sending untreated waste overboard. It also means one less thing in it to fail and/or require maintenance. Since the Lectra/San has been around for 30 years now, and some of those original units are still in service, it's obviously a design that works exceptionally well. And btw...the PuraSan works the same way.

As for whether it will work with a gravity toilet...I've emailed Vic Willman, tech services manager at Raritan who's been there 30+ years and knows EVERYTHING about Lectra/San, for an explanation, 'cuz it doesn't make sense to me that it wouldn't work with a gravity toilet. Incoming from any source has to displace an equal amount that's already in it...and it only has one place to go: out the discharge. So WHY would it have to be pushed overboard by a toilet pump????

Either you got some wrong information, or I'm about to learn something new. If I am, it won't be the first time, and isn't likely to be the last time either.

how would water flow freely out the sea/cock without some pressure?
as the pressure against the outside of the sea/cock is = to the weight
of the boat in the water? If there is no pump in the lectra/san, and no
pump in the head, and no pump anywhere else along the line, there
is no way the weight of water from the toilet is going to do it. now
maybe is it flowed out above the water line, and everything flowed
downwards, it might be workable.

thank you
Jason Miller

I had two Purasans on my 14x72 Jamestowner houseboat - I had to remove them because they aren't legal for the length of the boat and the lake/marina I moved it to. But, they work like the Lectrasan and they work as Peggy explained. Your physics are off a little - the entire weight of your boat is not balanced on the toilet's through hull opening - it is distributed across the entire boat bottom. So, while there is some water pressure present, the outflow from a Lectrasan (when installed properly) will work through a bottom mounted through hull.

Here is the _link_ for the Lectrasan owners manual:

http://www.raritaneng.com/pdf_files/lectrasan/L270v0404.pdf

there is no outflow created by the lectra/san, it has no pump ,
here is what happens, you pump into the lectrasan with the toilet, it
goes from one chamber to another, then the next time you use the
head, you pump it again, the force from the toilets pump not only
pushes the current waste in, but it pushes the waste from the last use
out. the lectra/san or purasan moves nothing on its own. it is a
simple flow through box, with one motor that turns the macerator
blades, and one that turns the mixer, thats all there is to it. a gravity
toilet uses no pump, it would be like hooking a hose to the seacock,
holding that hose in your hand and trying to poor water into it, the
water would never leave the hose as it would not have enough force
to open the oneway valve in the sea/cock that is being pushed
against by the water under the boat. but yes you are right that it is
not the full weight of the boat. however its more than the weight of a
gallon of water.

here is a quote form the pdf you posted

"How it works -
Each time toilet is flushed an equal amount of previously
teated waste is discharged. The Lectra/San does not pump
waste out, the flushing action of the toilet moves the waste
through the Lectra/San."

no if there is a waste/macerator pump that kicked on when the waist
water hit it, then off once it was through, then it could be installed
under the gravity head, and pump the waste into the lectra/san and
out the boat, I haven't found one if they make them, if anyone knows
of one please let me know.

also, do you still have the two purasan units? if you do, do you wish
to sell one?

Thank you
Jason Miller
www.wafflefilms.com

I just talked to Vic at Raritan...and did indeed learn something.

The Lectra/San and PuraSan will work with a gravity toilet if the thru-hull is above the waterline, but any line connected to a below-waterline thru-hull will have water in it to the waterline... there isn't enough pressure from a gravity toilet to overcome the resistance created by the water in the line...waste will back up.

So unless you want to either discharge above the waterline or settle for a holding tank, you're gonna have to pick another type of toilet. Vic doesn't think the SeaEra can support your weight...said the Crown II would have a better chance. The Atlantes definitely would, but it's about $800 at discount...any other household _style_ one-piece china bowl/pedestal marine toilet is in the same price range.