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Has anyone ever installed a ballast puppy system with the fill/empty line connected to the top of the bag instead of the bottom? On the two I have done, we installed the fill/empty line on the bottom/side of the bags. This worked fine. Howver, I was thinking that if one were to install the fill/emptly line on the top of the bag, the pump would not have to work as hard on fill cycles (or fill faster). This assumes that there is a check valve on the vent line. Has anyone experimented with this type of setup?
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Now
2000 SAN
Previously
1999 Air Nautique
1996 Tige Pre-2000
1989 Lowe 24' Pontoon / Johnson 100HP outboard -
I have thought about this before also, however, it seems like the pump still has to work against the head pressure to raise the water up to the top level of the bag (i.e., P = p(g)(h) --> the water in the line will generate a similar pressure to the water in the bag, and during the fill cycle you may actually be raising the water up and over into the bag which may create a slight higher pressure than the water level that is in the bag....of course there are all sorts of other variables, but these are my quick thoughts and it seems like it could hurt empty more than it could hurt the fill cycle. -
I do it this way when using impeller pumps but I don't think it really matters with impeller pumps. They still have to overcome the same head height whether they are pumping from the bottom or the top. Maybe even a tiny bit more if pumping from the top (assuming no pressure in the bag/tank).Comment
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I guess I was thinking that in a 750, with the bag getting close to full, that would add a lot of pressure on the pump. Maybe it is all child'splay for the impeller based pumps. Hose layout is better if I go on the bottom... just thought I might get some performance increase on the top. I guess I could always be the guinea pig and test them. I probably have the extra hose to do some trials... once I get the system installed anyway.Now
2000 SAN
Previously
1999 Air Nautique
1996 Tige Pre-2000
1989 Lowe 24' Pontoon / Johnson 100HP outboardComment
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I think the key is to remember that pressure is a result of depth, not the amount of water in the sac - that is, the height of the highest point of the water's path (e.g., in the hose or the highest point in the bag) dictates head pressure. Once the bag is close to full, you are going to have similar additional pressure across the extremities of the bag.Originally posted by Chexi View PostComment
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Okay. I'm no expert on fluid dynamics, but I think I learned something today. The amount of water in a tank is irrelevant (as long as there is some) in determining water pressure. It is the height of that water that determines water pressure. Thanks. This makes my ballast system cheaper, easier, and more convenient.Now
2000 SAN
Previously
1999 Air Nautique
1996 Tige Pre-2000
1989 Lowe 24' Pontoon / Johnson 100HP outboardComment
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Mine have been installed on top from day 1.........works fine.Comment
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