Air vent from main water tank seems clogged

The shop vac should suck/or blow enough air that it would be heard at the vent. I use a shop vac to blow up my dingy and I was quite surprised at how much pressure it can build.
 
I told you it was off the wall suggestion

Unless you have a commercial grade shop vac I'm not sure it would be able to make it pull that much of a vacuum.
Go back to post #23, he has already verified no blockage in the vent hose, the vent thru hull, and the tank fitting. As far as needing a commercial grade shop vac to suck water out...it doesn't take much vacuum. You must have been a good kid and not siphoned the gas out of the neighbors car.:D
 
One other thing to try. Requires little effort. Go to hardware store and get length of semi rigid plastic hose that is smaller diameter than vent hose. Remove the through hull fitting and run enough of the hose through the vent hose to reach beyond the vent hose connection and into the tank. Thought would be this would either dislodge something in the way of the vent fitting on the tank or hopefully go beyond it and allow air to move both ways. Another thought, with fill cap OFF, try compressed air through the vent hose. This is certainly a puzzle that needs closure.........
 
I told you it was off the wall suggestion

Unless you have a commercial grade shop vac I'm not sure it would be able to make it pull that much of a vacuum.

Actually Blueone is correct that any fresh water tank I have ever seen is top connect unlike the bottom connect of the pump out. So nothing would pump out the water.

MM
 
Taking a break from this project because I don’t think I am at risk of tank implosion when using the water and I know I can fill up to 3/4 without tank expansion. I agree this needs closure but I have limited help from my friend (who is handy) and we need to get onto new projects.

Apologies for a topic change but I’m pretty pleased about the space I opened up by removing the v berth bolsters. Next I plan to wrap padded vinyl around the exposed ledge and down below the mattress area. Have seen many threads about v berth expansion but no good “after” pics. I promise to post mine once I’m done.
 

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Sorry Jeff... I don't think you understand how this forum works. After you reach 3 pages of possible solutions your now in a legally binding contract that requires you to see the task at hand completed. Losing your handy man will not exempt you from this :)

Actually Blueone is correct MM
Hey!?!... that comes across as surprised or dumbfounded?... we are talking about a box with a hose attached to it.... everyone is right :)
 
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Sorry Jeff... I don't think you understand how this forum works. After you reach 3 pages of possible solutions your now in a legally binding contract that requires you to see the task at hand completed. Losing your handy man will not exempt you from this :)


Hey!?!... that comes across as surprised or dumbfounded?... we are talking about a box with a hose attached to it.... everyone is right :)

To quote someone who once said, "don't think you understand how this forum works", not everyone here gets a medal... LOL

MM
 
Hi guys, I’m the OP on this. I’m almost two years into owning this boat and I’ve had no issues with my workaround of filling the tank 3/4 full to avoid tank expansion. However, I’m running low on projects and this one is still on my mind. Feel like I let all of you down by not solving this in 2018 so stay tuned. I’m working up to going after this one again. Seems like it should be so simple!
 
Hey Jeff I have a 03 420 Sundancer it does the same thing. it seems to be a common problem on my model boat. Most people I have talked with have done everything to solve this and nothing helps it seems like tank is a little weak. Most people are doing just like you and I and only filling tank three quarters. I have heard of tank rupture in one case. Good luck.
 
watching with interest, as the same thing happens in my 310. i.e the tank swells as it nears capacity. This is probably very common, but most folks never uncover the tank and discover it unless they are tracking down another problem.
 
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I'm sure this was already mentioned, but I didn't take the time to re-read it all again... If the tank is expanding, air is not coming out (vent system is clogged). That's about all it can be. Fluid in/air out.

It could be the tank fitting (low on the "likely" list)... the hose being clogged (or a low spot where fluid has collected) or the vetn fitting, itself.
 

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