surf ballast (piggyback) with upright hard tanks (spoon?)

Anybody fitted piggy back ballast (surf bags) to a v-drive where the bags lie next to hard tanks?

boat is a matrix expression MVS - Aus made and designed boat.

I am pretty sure I have worked it out, but would be very interested in what has worked for others.

I am thinking the stock pumps , a couple of "Y" fittings ("WYE") and a tap to avoid filling the surf bag when not using.

boat has reversible pumps on hard tanks at rear.

the only real difference to normal is the tanks are on their side (upright) and the bag will lie next to them not on top (not really piggy more a spoon).

I plan to do it with a Y valve on the fill side so I fill the tank (to overflow) then swap to fill the bag (to overflow).

(there are no gauges so filling the tank to overflow will be important for when wakeboarding - most of the time).

from my drawings the vent is easy though I I am concerned that some water might run into the back when filling the hard tank (cant use 1 way valves as they won't breath?).

will probably run a vent tube through the centre of the bag so it cant fold and vacuum and suck the gizzards out of the pump.

cheers.

Forgive me if this sounds crazy(I'm a few coronas in) but why not run the y right off the pump and fill and drain them both at the same time?seems like filling one tank then going to the other would create more of a problem when draining

Originally Posted by bass10after

Forgive me if this sounds crazy(I'm a few coronas in) but why not run the y right off the pump and fill and drain them both at the same time?seems like filling one tank then going to the other would create more of a problem when draining

I have spent multiple corona's considering the design so no need for forgiveness.

my current plan is PUMP to Y valve then to either bag or tank.

the only real reason for this is so as I can fill TANK and then separately BAG - yes it makes it a two step process

I need to be able to isolate the bag as I will only use when surfing.

another option is

- PUMP to plain Y splitter (not a Y valve)

- Y to tank &

- Y bag with an inline valve (so I can shut off bag)

the only problem I saw with this is that I might fill one and then have water coming out the overflow when trying to fill the other?

that said, having looked a bit more carefully at the venting I think it should be ok as the top of the tank is higher than the bag will be so the bag should fill first?