Peggy, I've searched all your articles and archives, but can't find discharge hose-to-pump installation discussed. Please excuse me if I overlooked it. I believe I built a Peggy Hall dream system on my 35' Wauquiez, but it still stinks (!): Simple Groco manual head, white PVC flexible 1.5" hose direct to top of a custom polyethylene bow tank I had built, 3/8" thick, triangle-tapered in 2 dimensions to match both the vertical flare of the hull, and the normal reduction in beam as you go forward. Because of the efficient use of space, I calculated it to be about 32 gallons, but only takes up the usefull room that an off-the-shelf 15-gallon rectangular tank would. Two 1" vents, one forward, one aft on top of tank; Groco 1" full-flow 90 degree tail pieces (West Marine). 1" PVC flex hoses sweep upwards to deck, one port, one starboard side. I used 1.5" PVC 90 elbows as cowls, one points forward, one aft. Stainless screen prevents insect. (I made plastic 'donuts' to connect the 1.5" elbow to the 1" hose.) I of course use K.O., and flush dry,dry,dry; initial flush strokes you can hear the water splashing into the tank, then flush hard so last 5 strokes are pure air. The discharge 1.5" hose goes from the bottom of the tank up to a Henderson diaphram pump at the level of the top of the tank, then out and down to a 1.5" seacock. No vented loop since the seacock is only open during a 3-minute pump-out-at-sea session. The odor slowly increases day after day, and seems to be coming from around the pump. I am so frustrated, I want to drill a hole in the top of the pump to install a vent line with a ball valve to block it during pumping. You say there are truly odor-free systems, is there a trick in this final link of the system? Last Note: if I pump out completely, then flush with 20 gallons of water, then empty, there is no odor for a week; it only starts with the first use of the head, even though the discharge seacock remains closed and the pump unused. How can this be? Thank you very much, Dean