Back Pressure - Air Vent or Scaling?

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lakenorman285

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Nov 1, 2009
6
in the market for a Hunter 285 Lake Norman
Peggy -

I am fairly new to sailing and still learning the ins and outs of my 1985 H 285.

Yesterday, I stopped by the marina to check on the boat and noticed that the bowl had fillled back up to the brim with waste water from our outing the previous night. I proceeded to pump the head until all the water was back in the holding tank. At that time my son mentioned to me that he saw water coming out of the vent up near the toe rail. I figured that the holding tank was full and took it to the marina to have it pumped out.

The holding tank was pumped without an issue and it was FULL. I have noticed that when I now go to pump the head, it is easy for water to enter the bowl, however; I encounter some backpressure when I go to clear the bowl.

Do you know why the backpressure exists? Is it possibly a clogged vent hose? After reading some of your posts, I decided to spray water down the vent hose thinking that it may be clogged, but it seemed as though I heard the water hitting the tank - so I believe it is ok.

To be sure that the vent hose is not clogged, is it ok to use the pumpout pump on the vent hose to clear any obstruction if one exists?

Also, this boat has been in salt water for the last 25 years. The boat has now been in fresh water for two months. By putting fresh water in the holding tank, has this caused all of the scaling to decompose possibly clogging the lines??

Thanks for your help. Your comments are invaluable!
 
Peggie Hall HeadMistress

Peggie Hall HeadMistress

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Dec 2, 1997
8,949
- - LIttle Rock
Make/model/age of your toilet?

To answer your question...yes sea water mineral buildup can block the head discharge hose. Fresh water wouldn't "decompose" the buildup...the buildup can accumulate till it first starts to create backpressure, then blocks the hose altogether (see photo)...but I don't think that's your problem, 'cuz you didn't have a problem till you let the tank get so full it was overflowing.

It MIGHT just be a coincidence...'cuz if your toilet is a Jabsco, there's a very common problem with 'em: the wet/dry cam fails. It hangs, creating resistance to pumping that feels like backpressure. Try jiggling the lever to see if that helps...if it does, that's your problem. The cure: replace the wet/dry cam assembly (or buy a decent toilet!).

If it's not blocked discharge hose or a failed wet/dry cam, about the only thing left is a blocked tank vent. Check both ends of it. I don't think there's anyway for a pumpout hose to clear it...I'm not even sure how you could try!
 

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lakenorman285

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Nov 1, 2009
6
in the market for a Hunter 285 Lake Norman
Peggy -

thank you for your help. Yesterday I pumped out the head again without any issues. I think you are right.... I need to switch out the head with a new unit. The current unit must be 10-15 years old and the cam switch is dead.

Thanks,
 
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