Air Not Venting From Sacs

[Coop]

I have an RZ2 with surf ballast. I swapped out the rear OEM sacs for the plug-n-play cube sacs. When I fill the sacs, I'll often get an air bubble in the top of the sacs. No big deal - the air should just vent out as the sacs fill, right? Problem is the air will stay there, even when the bag gets full - to the point that the sac gets so tight, I need to stop the fill because I'm worried about breaking the sac. Water will start coming out the drain line (I assume it's being forced out because of the pressure), but the air is still in the sac.

My question is why does this happen? Shouldn't the air just easily exit out the vent line as the sac is filling? Isn't that just an open line from the bag to the thru hole?

I do notice that, if I leave it and surf for a bit, the air seems to eventually exit, but I don't understand why that's not happening as I fill the sac.

[mls6722]

I have a check valve on my vent line and my sacs do the same. It takes a significant amount of pressure to open the check valve. When my sac is nearly full, I disconnect the vent fitting at the sac and burp the air out.

[Ewok]

It also depends on the location of the vent fitting on the bag, is your vent in the middle of the cube where the air bubble is? If not the air won't vent. I had to play around with different locations for the vent until I found that the center top of the bag is best for the vent in my setup.

[Coop]

Thanks for the replies.

I have a check valve on my vent line and my sacs do the same. It takes a significant amount of pressure to open the check valve. When my sac is nearly full, I disconnect the vent fitting at the sac and burp the air out.

Anyone know whether the factory-installed systems have check valves on the vent lines? Seems strange that they would require that much pressure to open.

It also depends on the location of the vent fitting on the bag, is your vent in the middle of the cube where the air bubble is? If not the air won't vent. I had to play around with different locations for the vent until I found that the center top of the bag is best for the vent in my setup.

The vent fitting is on the top of the sac towards the rear. Same place as in the OEM sac. It seems to be in the area where the bubble is, so I don't think that's the problem (although I think it might have been better if they had put the fill line at the rear and the vent line at the front because air bubbles will tend to travel forward when the boat is weighted down in the rear).

[IDBoating]

This can happen if your vent line has a bit of water in it that cannot get out - sort of like a sink trap, where the hose "dips" a bit and traps some water. The air pressure isn't enough to force the water up and out of the valley, so air cannot escape via the vent anymore.

Just a thought.

[Coop]

This can happen if your vent line has a bit of water in it that cannot get out - sort of like a sink trap, where the hose "dips" a bit and traps some water. The air pressure isn't enough to force the water up and out of the valley, so air cannot escape via the vent anymore.

Just a thought.

That might be the issue. I recently had my vent and drain lines re-routed to the opposite sides of the boat in an effort to stop some passive draining. The lines droop down a little across the transom, which could be trapping some water and causing the blockage. I'll have those tightened up.

Thanks for the feedback.

[IDBoating]

That might be the issue. I recently had my vent and drain lines re-routed to the opposite sides of the boat in an effort to stop some passive draining. The lines droop down a little across the transom, which could be trapping some water and causing the blockage. I'll have those tightened up.

Thanks for the feedback.

Hope it helps. Please report back for the benefit of all!

[barry1me]

Any updates?

[Coop]

Based on WA's post, we got rid of the droop in the vent lines by moving them up higher across space behind the engine compartment. The check vales seemed to be working ok.

Today was my first day out. Seems to be better. There's still an air bubble, but it's smaller. I think the remaining bubble is caused by the fact that the vent line fitting ends up in water before all the air can vent. Makes me wonder why they don't install the fill line at the aft fitting and the vent line at the forward flitting. As the bag fills and the back fhe boat sinks, the air will tend to move forward. I would think the vent might work better attached to the front, but maybe there's something else I'm not considering.

Thanks again for the replies.

[chpthril]

Makes me wonder why they don't install the fill line at the aft fitting and the vent line at the forward flitting. As the bag fills and the back fhe boat sinks, the air will tend to move forward

http://www.tigeowners.com/forum/showthread.php?t=17025

My thoughts exactly.

[NICKYPOO]

That is exactly why I had my custom sacs done with the vent on the side front corner of the sac. It works perfect. With it being on the side, the fitting doesn't get pushed down into the sac. Mike and I were in agreement on this the we ordered them and we were right.

[Coop]

Thanks, guys. That'll probably be my next mod.