I have a macerating electric toilet which discharges into a plastic holding tank. The tank is vented and there is a deck fitting for pump out. In addition, I have a Type I Sea-Land MSD connected to the holding tank through a shut off valve with a hand pump to transfer from the holding tank into the Sea-Land MSD. After processing, the Sea-Land pumps overboard. Would you care to comment on this system? I have posted a diagram at:

http://carlten.tripod.com/Sanitation/sanitation.html

The boat is 31-foot and normally operated in salt water inside the three mile limit. But I also operate in Canada where direct overboard discharge outside of harbours is legal.

Carl Tenning

"Q E Too"

I'm very familiar with your SeaLand Type I...it was originally called the TDX..then slightly redesigned and the name changed to SanX. SeaLand discontinued it entirely in 2002.

To use it legally as a Type I (treat and discharge) requires the use of a chemical called TDX...a nasty formaldehyde-_base_d witch's brew that could not be any LESS environmentally friendly (just dumping the tank has less negative environmental impact)....costs about $20 USD/gal...and only treats 4 tankfuls/gallon. TDX is the only chemical certified for use with it, so you cannot substitute any other chemical--including any holding tank chemical...so if you think any chemical you're using in your holding tank is actually treating the waste, you're mistaken.

How it's supposed to work: There should be a holder for the TDX gallon jug, which is connected to the tank by a hose that's connected to a pump. Waste goes into the tank--which holds 9 gals, btw--either from the toilet or (as yours does) from another tank...flip the "treat & discharge" switch which causes a pump to inject a pint of TDX into the tank and then starts a 20 minute macerating and mixing cycle...then a relay turns of the macerator and turns on the overboard discharge pump, which runs for 5 minutes...another relay shuts down the discharge pump and injects another pint of TDX, then shuts off till the system is started again.

If you are relying on a holding tank chemical, or using a chemical holding tank product and substituting something for TDS, I'd be very wary...mixing chemicals can produce toxic or even lethal gasses.

So...how ARE you using it?

Thank you for reviewing my sanitary installation. Yes, I do use the SanX TDX fluid in the gallon bottle. Pretty nasty stuff. I try to avoid breathing the fumes when changing a bottle.It sells here for $24 per gallon. A separate container holds the gallon jug and the pump.

The diagram I copied this from was the SanX manual which lables this a "Deoderant Pump". I will change the diagram to indicate it is really TDX chemical.

You don't ever want to use that system to dump your tank in the slip or in an anchorage (unless you want anyone within a mile of you to seriously consider hiring a hit man) ....'cuz the discharge is very upleasant to see and smell.   Nor do you want dump it when you're sitting anywhere, because TDX is a lethal chemical. I once had the TDX system on a previous boat...I only dumped it while underway at about 1500-1800 rpms in open water to spread the discharge over as large an area as possible in order to dilute the impact.

Yes, I wholeheartedly agree. However, I much prefer to use the shore side pump-out. Unfortunately there are not many of them available near where I moor. The nearest one is at a State Park dock and it is currently shut down for the winter. You'd think that the State would be more environmentally friendly. Many of us boaters here operate year around.