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sprfrkr
Newbie
Joined: 10 May 2010
Posts: 35
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 Posted: May 17, 2010 10:43 am Post subject: Two Puppys, One Thru Hull |
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| Hey all, I have a front and rear ballast system with two reversible Jabsco puppys, one for the front, one for the back bags. I am using a single through hull fitting with 3/4"id tubing that has a "T" fitting going to each of teh puppys. My question is, do you think there will be any issues filling the bags, especially if one puppy is running and the other is not? I am concerned that one pump will try to steal water from the other pump/bags! Also, if running both, do you think there will be any flow starvation issues given the size of the incoming line? |
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Broccoli B
Wakeboarder.com Freak
Joined: 12 Jul 2003
Posts: 2670
City: Grand Rapids
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| Posted: May 17, 2010 12:58 pm Post subject: |
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I would use a Y connection instead of a T
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Brent B
| jt09 wrote: | | don't assume what you think i assume. you would assume wrong. |
| lcap wrote: | | you assume that i assume that my assuming is wrong and assume your assumption therefore must be correct. |
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sprfrkr
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Joined: 10 May 2010
Posts: 35
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| Posted: May 17, 2010 1:03 pm Post subject: |
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| Ok, that actually does make sense. Would it make that big of a difference you think? Do other people run multiple pumps on a single thru hull? |
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Wakeboarder3780
Wakeboarder.Commie
Joined: 21 Oct 2003
Posts: 1334
City: Wausau
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| Posted: May 23, 2010 7:01 am Post subject: Re: Two Puppys, One Thru Hull |
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| sprfrkr wrote: | | I am concerned that one pump will try to steal water from the other pump/bags! |
I don't think this will be an issue. When the pump is off the impeller shouldn't turn and thus the other pump wouldn't be able to steal water from it. Of course I haven't tested it or anything but I can't imagine it would be a problem.
| sprfrkr wrote: | | Also, if running both, do you think there will be any flow starvation issues given the size of the incoming line? |
How big is the ID (inner diameter) of the pipes built into the jabsco pumps? Then take that inner diameter, halve it to get the radius, and run it through the area for a circle (PI*R^2). That's how much area each pump needs. Multiply it by 2 since you have 2 pumps. That's how much they both need.
Lets assume one pump's area is X. Area for both pumps is 2X. Your through hull needs to be big enough to support for 2X. Solve the following equation to get the size of how big your through hull should be for ID:
2X = PI*R^2
Solve for R and that's your ID of your through hull you need to be. Match up hose sizes to your through hull / pump sizes so you aren't letting your hoses strangle them.
After that you're fine.
Oh, and did you put in a shutoff valve right off of the through hull? One puncture in the lines you have and you won't be able to shut off the water.. Or even worse.. I blown pipe clamp.. now that's a LOT of water coming into your boat 
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sprfrkr
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Joined: 10 May 2010
Posts: 35
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| Posted: May 23, 2010 4:14 pm Post subject: |
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Wow, great response. I'm sure the math is easy, but that just hurt my head!
The thru hull is a factory thru hull with a 3/4" ID line. The thru hull is at the very lowest point of the boat hull in the rear. The pumps sit above water level. If my line breaks, will I have an issue with flooding? I would think the lines are fairly low pressure, but maybe I am wrong. |
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Wakeboarder3780
Wakeboarder.Commie
Joined: 21 Oct 2003
Posts: 1334
City: Wausau
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| Posted: May 24, 2010 4:07 am Post subject: |
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depends where your line breaks right? If it breaks anywhere below water level you're hosed. No pun intended. I did a ton of research into putting a ballast system in and didn't go with through hulls because finding a shut off valve was such a superior PITA.
The pain is mixing with 2 different types of thread. There was 1 system out there that solved the problem but I don't have the links anymore. Found it on a sailing site.
If the math hurts your head I'd guess the pumps are designed for a 5/8 garden hose. This leaves you with 3/4 for the through hull being "just about right".
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sprfrkr
Newbie
Joined: 10 May 2010
Posts: 35
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| Posted: May 24, 2010 5:11 am Post subject: |
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| Thanks bud. I'll let you know if I sink it or it works after this wknd. I appreciate the help. |
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