Sacs losing water ???

[MJO21]

So getting ready to surf yesterday and as we are filling up everyone jumps in for a swim. Bags start to overflow so I turn off pumps. Everyone hangs out in water for another 10-15 minutes before we surf. I check bags before we start to surf and the have lost about 25% of fill? Is this normal?

I refilled and we went surfing and I checked everytime we stopped for a pick up…and always lost 25-50%???

The locker where the bags are located are dry, so I assume it is going back out through the pump???? Or????

[jmoore15]

I would pull your bags and to make sure the fittings are properly sealed on your bags. I had the same happen to me and it turned out to be one of my fittings on the bottom of my bag.

[chpthril]

Common, but not a design feature. Passive draining does and can occur. What year and model boat? What ballast option? As noted, need to first make sure its not an actual leak, especially with sub-floor tanks or sacs.

After that, you need to start isolating the paths that passive draining can take, so you know which path its taking.

[scottspray]

Could be losing water through the fill pump also. Try putting a back flow valve in the fill hose after the pump, but before Y in the fill hose. It may make filling a little slower.

[NAstleford]

We were having similar issues and found a few things. Found hose(s) coming apart at the fittings between subfloor & PnP bags causing them not to fill fully and leak into bilge.
Also found leak on the fill line just past the check valve, was a nice hole once took the heat shrink off due to hose clamps. Bag would fill and overflow but then would drain back out through the hole in the hose.
Saw your other post about water in the bilge so sounds very similar.

[scottspray]

Are both rear tanks draining at the same rate? If so, hopefully it is passive and not a cracked subfloor tank.

[MJO21]

2013 z3. Surf ballast.

appears to me that both bags are losing water equally.

when I feel around the locker o do not feel wet spots.

[scottspray]

I have the same setup I think. Surf Pro with two 400 bags in front 600 on each side in back split between bag and tank. Had shaft packing replaced when I bought the boat a year ago. Had one crack in a subfloor tank where the drain pump attaches. It would fill the bilge and not drain tank completely. Dealer had seen it happen before. Plastic welded it. Replaced rear drain pumps while we were at it. I replaced my rear sacs with L shaped ones with quick connect and put check valves in rear fill hoses after fill pump but before Y in hose. There are two separate bags in front with check valves already installed. The fittings on the old bags come loose easily. I tightened all fittings on front bags and left the compartment boards off so I could keep an eye on bags. Check valves in front look factory.
Ice chest is a good spot for weight.
Shaper really helps.
Easy to get clean decent surf wave.

[BCRider]

As Chpthril said, passive draining is quite common especially with some of the larger fat sacs. Once the boat is at surf speed that sends a lot of water/pressure back towards the drain and vent lines. I've started using rubber corks on the side thru hulls to keep the water in otherwise, I'll lose most of it while riding.

[MJO21]

Can I just fill them with a garden hose through the vent to see if I get water in the bilge????

[scottspray]

If your going to do it on the trailer I would take the bags out then fill the tanks that way. Then fill the bags outside the boat. You could check for holes and loose fittings. You may need the bags out of the way anyway. When reinstalling make sure you put hoses back on the same fittings of course.

[Zackdogg]

At the invasive species station at Tahoe, they fill the ballast with a fake-a-lake, on the ballast pickup under the boat, and a hose, you could run pumps, and be able to see everything with the pumps running that way.


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