vents

spudski67 · Newbie Joined: 24 Mar 2006 Posts: 15 City: burlington

please explain how vents work, what the point is, and how to install them.

I am thinking about making a ballast system with a reversible pump.

thebulkhimself · Newbie Joined: 31 Mar 2006 Posts: 9

Without vents the air can't escape out of your ballast tanks therefore you get pressure build up in the tank and the pump can't feed water into the tank and therefore will cavitate(if you're lucky) or burn out. Same in reverse.

Your vent pipe should tap off the top of the ballast tank and preferably the entire pipe should be ablove the top water line in the ballast tank.

spudski67 · Newbie Joined: 24 Mar 2006 Posts: 15 City: burlington

so the vent doesn't need to go anywhere because it is just air? are vents built into the bags? i had thought a vent was so that the pump does not over fill and burst the bag...

spudski67 · Newbie Joined: 24 Mar 2006 Posts: 15 City: burlington

couldn't i just fill the bags the first time and "burp" any air out? it seems that after that i wouldn't have to worry about air.

is just occured to me that maybe you only need vents if you are using tanks, that would make sense to me... i will be using bags. am i right?

spudski67 · Newbie Joined: 24 Mar 2006 Posts: 15 City: burlington

one more thing...i want to pump in and out through the same through hull. the pump is strong enough that i won't have to worry about it being able to pump water back out through the bottom of the hull, right?

please help!

P hat in Cincy · Posted: Apr 12, 2006 8:43 am Post subject:

As mentioned above, the purpose of venting is to:
1) Let entrapped air escape the bag/tank in order to fill ballast with water.
2) Provide an overflow outlet in case a pump in adventantly left on.

Most would want the vent line to exit the boat. You don't want overflow dumping into your boat.

Vents are not built into bags. The vent should be at the top of the bag/tank and the vent outlet should be higher than full fill height of the tank/bag.

Technically you could just burp the bags everytime you fill them, but think what COULD happen the one time you leave a pump running on fill. Bags will burst...and that may be best case!

For a hard tank you would want an open air vent for filling and draining.

For a ballast bag you should use a check valve to let water/air out when filling. For emptying, if you don't use a check valve you'll run the risk of the pump sucking air and leaving some amount of water in the bag.

Look here to see how I did mine.
http://forums.wakeboarder.com/viewtopic.php?t=53991

DizzyG · Soul Rider Joined: 11 Jun 2003 Posts: 266 City: Oconomowoc

Put in vents! I used to run with just a fill/drain line and popped one and got a hole in another bag. Most of the bags now come with at least 2 holes to fill/drain/vent.

Try to put the vent on the high side for when the boat is running at an angle while pulling someone or you can end up with your water being drained out when your'e on plane.

You can burp them, but vents are easy and if you kill one bag you've already cost yourself more than the vents would have been in the first place.

spudski67 · Newbie Joined: 24 Mar 2006 Posts: 15 City: burlington

wow p hat that is awesome! that helps a lot.

i still do not understand why a check valve is needed on the vent line...
if it is closed and the pump empties the bag, a huge amount of stress will be put on the pump because it is trying to suck on something that is already empty. and if the check valve is open when draining, i can understand that i am running the risk of pumping air.

so, what I am thinking now is that i will have a vent off the top of the bag and t into the bilge pump line right where it exits the boat. don't they make pumps that can run dry, or shut off when they run dry? in that case, draining too much would not be a problem.

P hat in Cincy · Posted: Apr 12, 2006 6:16 pm Post subject:

spudski67,
Again, a check valve insures flow (of air and/or water) in only 1 direction. Typically, you only want air and water to leave and not come in. By not putting in a check valve you still may be able to empty most of the water out. PVC swing check valves are under $10 each, so it was a no brainer for me.

If you are planning on using an impeller pump, letting it run dry is not healthy whether it's trying to suck a bag thru the hose or sucking air thru the hose. The impeller will heat up and deteriorate. Don't rely on run dry protection.

I, personally, would not use the bilge vent line. 1) You would HAVE to put check valves on both lines so that the bag vent doesn't flow into the bilge and the bilge doesn't flow into the bag. 2) Most importantly, the bilge line is there to aid in getting water out of your boat in case of an 'event'. I wouldn't compromise it's primary function.