Piggybacking Fat Sacs?

[toomuchhype]

Although not a lot of people do it, there is a hybrid alternative to adding dedicated pumps and just piggy backing. The biggest hold up for most people on adding dedicated fill and drain pumps is drilling holes. If you want, you can use T connections on the bilge intakes for the existing ballast system and use Y connections on the vent and drain hoses to avoid drilling any holes. Personally, drilling holes isn't the scary part, but every thru-hull penetration is expensive due to the additional hardware required for each one.

My last system was dedicated pumps but I am contemplating trying one with 2 Johnson reversible pumps, and no new thru-hulls. I will probably use the rear drain plug to put in a T valve for the intake and drain, and then Y into existing vent hoses so that I don't pop the sacks and dont have to live the rear hatches to see how full they are. Just brain storming at this point...

Yep, that's exactly what I am planning. I'm going to T off of the fill pump under my middle/trans seat. Then for the vent/drains I will use Y-connectors. I have 1-way check valves ready if I need to install to avoid the draining of the sac via Y-connection from filling an empty tank via it's drain hose.

[scott_fx]

sorry if this has been stated but the thing im not understanding is why you're filling and draining from the same bag? wouldn't it make sense to hook the fill pump to the higher bag, have that drain connected to the fill line of the lower bag and then hook up the drain pump to the lower bag?