Strange thing with waste system

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Seevee

Guru
Joined
Sep 1, 2016
Messages
3,506
Location
usa
Vessel Make
430 Mainship
All,

At the marina, I was having a pump out and when I opened the opening to the pump out and the contents were under pressure and exploded out of the pump out tube throwing bad stuff over me and half of the boat.

Now, not sure what happened nor why. Doing the Loop and had the waste pumped out 7 days ago, which should have been fine with a 53 gal tank. Been than long before without issues.

Any ideas?
 
It sounds to me that the vent is plugged and causing the tank to pressurize.
 
+1 on the vent being plugged. Do you have a filter in the vent?
 
Sounds logical, thanks. Now, does anyone if the vent cap can be unscrewed or does one have to take the hose off at the other end and blow it out with air?

Typical vent:
 

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Should be on the outside of the hull right in line with the pump out hose/cap.
 
Sounds logical, thanks. Now, does anyone know where the vent is on a 400 Mainship? Thanks



It will be the opening on the side of the hull that isn’t anything else. You will have vents for your fuel tanks and water tank. Eliminate those and the other vent will be your holding tank vent.

You should also be able to see the vent hose on your tank and see which direction it is going. The vent will likely be on the side of the there. In my limited experience, the holding tank vent is usually near the pump-out opening. So if your pump-out opening in on your deck, look to the side of the hull below the pump out.

This is one of the reasons I like to pump-out my own holding tanks. I will always back flush the vent line when pumping out the holding tank. I pump out, then fill up the holding tank at least half full and pump out again. I’ll do a second rinse as well and this time while the tank is being pumped I will direct a stream of water over the tank vent. This gets sucked back into the tank, flushing the vent line to help keep it clear.

We don’t seem to have problems with wasps building nests in the vent line in the PNW so I can’t offer any suggestions there.
 
Thx for all the good info. Will try to force water thru the vent opening and see it that clears it. If not, suspect that I'd have to disconnect by the tank and flush out with air or water the other direction.

Other ideas?
 
when my diesel vent was stopped up, I removed the line from the through hull and cleaned the blockage in the fitting from inside .the line was fine
 
Thx for all the good info. Will try to force water thru the vent opening and see it that clears it. If not, suspect that I'd have to disconnect by the tank and flush out with air or water the other direction.

Other ideas?



Long flexible wire?
 
If you have a tank vent in-line filter, check that it is not clogged. You may need to replace this. It should be in the vent line, just before it exits the hull. If you have one, you will not be able to back-flush your vent line as this will clog up the filter.
 
I used a cut-off Harbor Freight sink router. To avoid any similar results to your pump-out fiasco, I’d use caution with air pressure or suction, especially if the tank is not clean. Methane can ignite in a shop vac, so I’ve been told.:eek:
 
If you have a tank vent in-line filter, check that it is not clogged. You may need to replace this. It should be in the vent line, just before it exits the hull. If you have one, you will not be able to back-flush your vent line as this will clog up the filter.

I would suggest that if the OP has a vent filter, he remove it. The need for a vent filter can be eliminated by proper maintenance of your holding tank. Plus, they prevent the back flushing of the vent line.
 
The vent LINE is rarely if ever blocked...unless it's clogged filter in the line-which happens when the tank overflows or you try to backflush the vent line--blockages almost always occur in the thru-hull and/or at the connection to the tank--both the vent fitting on the tank and that end of the vent line. So use a screwdriver, ice pick or whatever works to scrape out the thru-hull...knock out any screen, screens cause more problems they solve or prevent. Now that the pressure has been relieved, remove the vent line from the tank and scrape out the tank fitting and that end of the vent line.

You might also consider checking out the link in my signature...it goes to a comprehensive "marine toilets and holding tanks 101" manual that will help you learn how to prevent problems instead of having to solve 'em.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
 
The vent LINE is rarely if ever blocked...unless it's clogged filter in the line-which happens when the tank overflows or you try to backflush the vent line--blockages almost always occur in the thru-hull and/or at the connection to the tank--both the vent fitting on the tank and that end of the vent line. So use a screwdriver, ice pick or whatever works to scrape out the thru-hull...knock out any screen, screens cause more problems they solve or prevent. Now that the pressure has been relieved, remove the vent line from the tank and scrape out the tank fitting and that end of the vent line.

You might also consider checking out the link in my signature...it goes to a comprehensive "marine toilets and holding tanks 101" manual that will help you learn how to prevent problems instead of having to solve 'em.

Ahhh, but for the simplicity of a urine separating, desiccating head ;)
 
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The vent LINE is rarely if ever blocked...unless it's clogged filter in the line-which happens when the tank overflows or you try to backflush the vent line--blockages almost always occur in the thru-hull and/or at the connection to the tank--both the vent fitting on the tank and that end of the vent line.

I want to be sure I understand Peggie. Are you saying that normal backflushing of the vent line can cause a blockage or that trying to backflush an existing blockage that is at the thru-hull?
 
Why don't they offer a urinal for guys on boats? It would save a lot of water and plumbing aboard. There are even waterless ones, although I think you have to replace other stuff regularly to keep it from stinking...
 
Why don't they offer a urinal for guys on boats? It would save a lot of water and plumbing aboard. There are even waterless ones, although I think you have to replace other stuff regularly to keep it from stinking...


We have a urinal on our boat some otheres call it the duck board :D
 
Exactly. Are you going to try one ?

Got one, thanks :)

My comment to Peggy was a poke in the ribs “tit for tat” since she dropped into a thread of mine last year about desiccating heads with some negative comments.
 
Oh! I didn’t realize you had one. Like it?

It’s amazing how defensive folks get when you bring up these composting heads. But I guess that’s typical— if it’s something different/not well understood it’s human nature to attack it.
 
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Why don't they offer a urinal for guys on boats? It would save a lot of water and plumbing aboard. There are even waterless ones, although I think you have to replace other stuff regularly to keep it from stinking...

I use one of those small plastic ones like they have in hospitals. Put a little Noflex Digestor in it and there is no stink. When it gets full I dump it into the toilet and flush once. You can get one at any drug store for a couple of dollars.
 
An overboard urinal is an interesting idea.
 
I use one of those small plastic ones like they have in hospitals. Put a little Noflex Digestor in it and there is no stink. When it gets full I dump it into the toilet and flush once. You can get one at any drug store for a couple of dollars.





They dont make them big enough and deep enough for us Ozzies :D
 
Oh! I didn’t realize you had one. Like it?

It’s amazing how defensive folks get when you bring up these composting heads. But I guess that typical. If it’s something different/not well understood it’s human nature to attack it.

So far, so good :thumb:

I didn't want to hijack this thread...just meant to tease Peggy a bit.

Here's the most recent thread about 'composting' heads if someone wants to talk further about them;

http://www.trawlerforum.com/forums/s3/composting-head-info-38059.html
 
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Makes me appreciate our composting head on board. Weeks and weeks between emptying with my wife and I on board, no holding tank and hose issues, no plumbing, no thru hulls, no odor, no chemicals, and the little 12V computer muffin fan runs on less than 2 amps per 24 hours. :dance:

Don
 
I want to be sure I understand Peggie. Are you saying that normal backflushing of the vent line can cause a blockage.......or that trying to backflush an existing blockage that is at the thru-hull?

I just re-read my post and I see what I said that confused you..I worded it badly.

It's any FILTER in the vent line that can create a blockage if it ever gets wet, either from a tank overflow or back flushing the vent line. So a filter in the vent line makes back flushing it impossible.

You don't backflush the vent line to clear a blockage because the LINE is rarely if ever blocked...you backflush every time you wash the boat to PREVENT vent blockages However that requires a vent thru-hull that's open--"vent" thru-hulls are not...they're actually designed for use on fuel tank vents and also suitable for water tank vents because they're also designed to keep water out of the fresh water and fuel. So it's almost impossible to get enough water through one to do any good. But it doesn't matter whether a little sea water gets into a waste tank...what does matter is whether the vent is open enough to allow an exchange of air with the gasses that waste generate. "Bulkhead" or "mushroom" thru-hulls--the kind your bilge pump drains out of, that you can stick your finger into--do that. And they also allow you to stick a hose nozzle up against 'em and back flush the vent line all the way into the tank...preventing any blockage at either end. Any spiders or other insects that have tried to set up housekeeping in the vent line just get a water slide trip into the tank.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
 
Thanks Peggie, I just wanted to be sure I wasn’t completely off base.
 
Just to add to the confusion, I HAVE seen plugged vent lines (as opposed to the vent itself.) I suspect the PO over-filled the tank and forced waste into the vent line with every flush, after which it hardened in place. (Sorry for the graphic visual there!)
 
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