Holding tank

Greg Dudzinski

Greg Dudzinski

New Member
Feb 25, 2021
6
Westbrook, Connecticut
Boat Info
280 Sundancer 2002, Raymarine GS125
Engines
Twin 5.0 w/Bravo III Drives
I just went down to my boat to get it ready for the season. I noticed that my holding tank was bulging up - not sure if it froze over the winter but it has antifreeze in it and it doesn’t look like it it cracked. Has this happened to anyone else?
 
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Was it pumped out, flushed, pumped out again and then winterized?
You should complete your user profile with your location as many times the location you boat in can have an effect on all kinds of questions about different boat systems.

Welcome aboard CSR.
 
The vent may be clogged and now that it's getting warm out, the tank could have expanded.
 
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I have never seen this before. Maybe the gases built up and couldn't get out. I try to pump mine out as part of winterization.
 
mrsrobinson said:
I have never seen this before. Maybe the gases built up and couldn't get out. I try to pump mine out as part of winterization.
Click to expand...

I have but for a different and perilous reason.

Wasps built a nest in the vent. The vacuum pump kept pressurizing the tank and was like a ripe melon. Looked more like a pillow than a cube.

Had I not glanced at it while in the ER, it would have erupted all kinds of mayhem at the onset of my next pump out.

The tank can't expand if it's vented. Look there first.

Crack the pump out deck fitting and see if gas escapes, then clear the vent.
 
I will check on the vent this Sunday when I get back down to the boat. I did have it pumped out before winterizing.
 
Second on Crack the deck vent... if thats it then your vent line is obstructed.
 
Just to give an update - I went to my boat yesterday and removed the waste cap, this did not relieve any pressure in the holding tank and I was unable to push it back into shape. The boat is going in the water this Friday - not usre if maybe the vent filter is clogged?
 
Greg Dudzinski said:
Just to give an update - I went to my boat yesterday and removed the waste cap, this did not relieve any pressure in the holding tank and I was unable to push it back into shape. The boat is going in the water this Friday - not usre if maybe the vent filter is clogged?
Click to expand...
Pop out one of the depth sensors on the tank it self…. Just rubber grommets …. That should tell you what’s going on

pics would help too
 
The vent could still be clogged and it initially caused the expansion. But this particular expansion ended up "locking in place" and the built up pressure eventually subsided but the expansion stayed. Remove the filter and vent at the tank and check/clear the hose... do the same for the filter (or replace/re-build if it's clogged).

Push harder on the tank... try laying a piece of wood on the main bulge area and use hammer. Or (with the blower running and good ventilation) gently heat the bulge area with a heat gun. You're working in a gas bilge so make sure there are no gas fumes.

Being in the water soon doesn't affect anything. The fix is the same whether in or out of the water.
 
It's strange that the tank held the distorted shape.

From here on, I'd disconnect things gradually and be prepared for the worst. A sewage explosion in the bilge is not something you want to deal with...worse in the water than out.
 
Wood/hammer/heat... concentrate it on the vertical section of the tank where the main bend is. I'd even try pushing IN at the vertical to horizontal 90* part.
 
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