Piggyback ballast question

[nickj03b 0]

Having a tough time figuring out if this will work,  seems like it would but nothing is ever that easy for me.

08 Avalanche with stock center tank, aerators for both fill and drain.

Want to piggyback a 370lb tube sac under port seat off center tank.  I was told if I used vent line off center tank to fill tube sac and then connected other port from tube sac to  existing vent line/thru hull this would work.  However I read somewhere there could be issues with the draining and negative pressure in the center hard tank.  Will this work and if not how can I make it work?  

 

Thanks!  

[Wylie_Tunes 146]

Getting the sac to fill, is the easy part, but will be about 2x the current fill time. Draining is the issue when the supplementary sac is on the same plane as the hard tank.Aerator pumps push water, they do not suck water. The issue is getting the water to exit the sac into the hard tank. Even a short direct link between the sac and tank, will leave water in the sac.

If you route the tank vent to the sac as make it a sac fill line, the tank will likely tin-can on itself when draining. The hard tank needs to freely vent. 

Best advice, remove the tank and replace with a larger sac.   

[nickj03b 0]

Thx for the reply.  The center hard tank is below the floor and the tube sac would be above the floor under port bench.  Would this elevation difference allow the water in the tube sac to flow back into the hard tank while draining.?

 

not sure what you meant about removing tank and getting bigger sac.  My main reason for doing this is so I can have another 370lbs on the port side for surfing.  I have rear bags as well on their own pumps.  

[Wylie_Tunes 146]

The get bigger bags, or bag, so you wont need that 370 in a separate sac. 

[wheels 151]

7 hours ago, nickj03b said:

Thx for the reply.  The center hard tank is below the floor and the tube sac would be above the floor under port bench.  Would this elevation difference allow the water in the tube sac to flow back into the hard tank while draining.?

 

not sure what you meant about removing tank and getting bigger sac.  My main reason for doing this is so I can have another 370lbs on the port side for surfing.  I have rear bags as well on their own pumps.  

In therory yes it will work. It will be very slow. To fill and even slower to drain. As long as your sac is above your center tank it will gravity drain into your hard tank and then drain through your hard tank. You will never get all the water out of your sac though as it will only drain to the fitting level which is not in the bottom of the sac. Save yourself a lot of headache and plumb in a impeller pump, it is not hard. 

[nickj03b 0]

10 hours ago, wheels said:

In therory yes it will work. It will be very slow. To fill and even slower to drain. As long as your sac is above your center tank it will gravity drain into your hard tank and then drain through your hard tank. You will never get all the water out of your sac though as it will only drain to the fitting level which is not in the bottom of the sac. Save yourself a lot of headache and plumb in a impeller pump, it is not hard. 

Thank you for this info.  Makes sense regarding being slow etc.  I will try it out and plan for the better setup this winter.  I have done impeller pump installs before just didn’t want to dive into that at this moment.  Thx again 

[Troy 234]

I have an 08 Avy also. the fill on mine is an impeller pump with empty being on an aerator for the center. 

I recommend a custom sac that fill the locker and under the seat, all at the same time. I have a custom starboard sac and it is awesome! You can get a lot more ballast with custom and they are not that expensive. I have a dedicated impeller pump for fill and empty and the factory system supplement the fill.  

[knotguilty 6]

I have the setup that you describe in my '05 Avy. It works fine.  The only issue I have found is the tank above the seat drains into the lower tank slower that the pump can pump out.  Just means that I check that the center tank is empty before I pull out.

[Jake707 171]

Pulling out after the tank is empty seems too late in my experiences........

[nickj03b 0]

Hahah true story on pulling out too late....

ideally a custom sac that extends from back locker to port bench would be best but of course my wife surfs goofy and that seems like it be a pain to try to fill bag only partially.  Plus I already have sacs plumbed in back there