Single fill drain hole vs. individual fill drain holes.

[jbgp1200]

I'm really torn as to which route to take with regards to drilling the thru holes in my boat. I really like the idea of drilling fewer holes in my boat then are necessary but I'm getting conflicting opinions on this from a couple of reputable sources.

Currently have no automated ballast and I am planning on installing 3 reversible pumps. Now the question is do I drill 6 houses or 4 holes in my boat to accommodate the fill/drain and vents? Ideally I want to drill the fewest number of holes that I need to but I want it to work right as well. I've been told that I can get away with a larger fill drain hole in the bottom to accommodate the draining and filling for all 3 bags. Great, that leaves me only drilling 4 holes in my boat and I love the idea. However I've also heard that this will put more stress on the other pumps when filling and draining at the same time and shorten the life of those pumps. Not sure I completely understand the physics on that as its water in and water out and I don't see how they would be struggling it the hole was large enough to accommodate the flow. But I want to confirm before I do this wrong and make a mistake.

Please let me know your thoughts.

[Thegerman618]

Talk to CHPTHRIL he's the man when it comes to ballast!

[chpthril]

Did we talk on the phone last week? You are going to get a number of varying opinions, doesnt make any one of them wrong. Im usually prepared to give additional info when I make a ballast recommendation. This might be based on my experience, feedback from one of my many ballast customers, or basic facts based on specs.

If you like math, you can take the flow rate of a pump and the flow rate of the proposed fittings, and calculate how many pumps a given fitting ID can support. Even further, we will have the weight of the hull working in out favor. These fittings are going to be below the water line in the hull of a 4K lb boat. That displacement is going to be forcing water into that thru-hull, further adding the supply.

Id say that at least 90% of the ballast setups I do (about 10-12) a season), are dedicated surf systems. This means that in most normal trips out, you will likely only have one rear sac filling and one front sac filling at any given time. So take that calculation you did, and adjust it by 33% because you will likely have one less pump drawing from that common manifold. Nothing wrong with using a single dedicated thru-hull for each pump, but may disagree with many of the reasons given to NOT do a common manifold.

Some are lukewarm on venting, but not me. I think every sac should have a vent. Even an aerator pump can build some decent water pressure in a sac. Further, the vent lets any trapped air purge and gives you an audible and visual indicator that the sac is filled.

[jbgp1200]

Hey Mike,

Yes, we spoke last week. Got my custom sacs Friday. Thank you for getting those to me so quickly.

I'm still just a bit conflicted on the best way to go about this but it seems that you have installed more then anyone so you would know. Is there any truth the the increased wear and tear on the pumps with a single drain fill? Will the impellers still last just as long with a single fill/drain hole?

Also do you have any photos or diagrams showing where the single fill hole with a 3 way T fitting and the pumps will go in an RZ2?

Thanks,
JB

[chpthril]

Is there any truth the the increased wear and tear on the pumps with a single drain fill? Will the impellers still last just as long with a single fill/drain hole?

I wont say its false, but I have not seen the logic explained in enough detail for me. I just dont see it happening in all cases.

The best resource for pics, is going to be this site. The cool thing is, the V, Ve and RZ boats all about the same once you pull the floor section up. Usually plenty of room between the fuel tank and v-drive on either side of the keel for a through hull. With the single setup, you just want to make sure you are behind the floor section, under the seat box, so height is not an issue for the hoses to exit.

[lee]

With reversible pumps and a manifold, what will happen if one wants to fill one tank and empty on tank at the same time? Seems to me that a dedicated hole for each pump would be less restricted.

[chpthril]

With reversible pumps and a manifold, what will happen if one wants to fill one tank and empty on tank at the same time?

the sac you want to fill, will fill and the sac you want to empty, will empty. There is no restriction.