I already have the dometic 975MSD, but i did see the thetford for sale on amazon for $140 and am willing to go that route if it is better. I do plan on connecting the MSD connection. For the thetford i noticed that the MSD pump out fitting comes straight out of the waste tank and connects to the sanitation hose without any twists or turns. For the dometic 975 I noticed that the msd connection makes two 90 degree angles coming out of the waste tank before connecting to the sanitation hose.Thetford discontinued the 550P (MSD version of their 550) several years ago. The Dometic 975 is the only MSD portapotty still sold in the US (or anywhere else that I know of)....fortunately excellent quality.
However if you possess any "handyman" skills at all, it's fairly easy to turn almost any portapotty into an MSD version, thanks to a li'l gizmo called the Uniseal UNISEAL
--Peggie
I was just curious if this would make pump out a little more difficult for the dometic 975 since the waste has to travel through two 90 degree angles straight out of the waste tank as compared to the thetford 550P.