Strange thing with waste system

[Dougcole]

Sevee,

The holding tank vent on the Mainship 400 comes out of the front of the tank (bow end). It's accessible from the small floor hatch in the V berth. It goes forward on a 90 degree fitting, then goes to starboard, then turns toward the stern under the floor of the bathroom, then goes behind the air conditioner, turns to starboard again, goes up the gunwale to the vent. Makes sense, huh?

I've never seen a more ineffective and poorly designed system.

Remove it all and run a vent forward, straight, no major bends, slightly uphill, 1" line, next to the anchor locker drain.

Here's a picture of what my 90 degree fitting looked like. PLUGGED! The picture doesn't show that it's totally plugged at the bottom. Really really smelled foul!

Jeffrey Guttenberger
R Time
2005 Mainship 400
View attachment 75597

This explains a lot, thank you for posting Jeffrey.

I've been having issues with my tank not properly venting. We get a puff of odor outside the boat whenever we flush. I know it needs more airflow, but I wasn't sure how to do it.

The screen on my vent through hull was clogged/rusted/too small, so I replaced it with an open through hull. I had to put a pie plate in the hull liner in order to get the through hull out. It has helped some but not enough.

I thought the vent line ran to the aft end of the tank but could never find it. I now see why.

Eventually I think I'll do the same as you, run a new line. But I have a big trip coming up in a few weeks, without time to make that change, so maybe I'll just replace the filter to get me through this trip. Was the filter obvious?

Thanks,
Doug

 

[siestakey]

The holding tank vent on the Mainship 400 comes out of the front of the tank (bow end). It's accessible from the small floor hatch in the V berth. It goes forward on a 90 degree fitting, then goes to starboard, then turns toward the stern under the floor of the bathroom, then goes behind the air conditioner, turns to starboard again, goes up the gunwale to the vent. Makes sense, huh? I've never seen a more ineffective and poorly designed system.

I have, including one vent line with a 360 degree loop in it. Boat builders have always been, and continue to be, the WORST sanitation plumbers on the planet! The only thing they did right in this one was put the vent fitting on the bow end of the tank.

Remove it all and run a vent forward, straight, no major bends, slightly uphill, 1" line, next to the anchor locker drain.

Yes! And use an open bulkhead thru-hull.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

Peggie we have helped so many upgrade vent lines amazing most are undersized

 

[HeadMistress]

Peggie knows about one. She turned me onto one several years ago. I don’t remember the name of the company anymore.

You're referring to the Uniseal UNISEAL which is the only thing to use on plastic tank. But whether it can be used in a fiberglass tank depends on how thick the fiberglass is. Give Aussie Globe a call to find out the max thickness on which it can be used. If the top of your tank is too thick, the answer will be to "cement" a male hose connector into it instead of a female threaded fitting. Whichever you use, this would be the perfect time to upgrade the vent line and thru-hull to at least 1".

Woodlord said, The sending unit for the tank level indicator can be ordered with or without vent in it I would get one with vent and clamp the vent hose on it

The best tank level indicators are the Profile gauges Profile Tank Monitors which use senders that go on the outside of the tank. Because they never come in contact with the tank contents, they can never become clogged by the animal fats in waste that requires removing the sender to clean it manually.

siestakey, builders use 5/8" vents on waste tanks because that's been the standard size for fuel and water tank vents since long before there were waste tanks. Since it never occurs to 'em (nor do they care), that unlike water and fuel, sewage has be managed. It costs 'em less the use the same size hose and same type of vent thru-hull on all tanks, so they do. Nor do they pay the slightest attention to how far most toilets can move bowl contents, so they'll use one holding for two toilets at opposite ends of a 40' boat and then, in a misguided attempt to direct odor away from the cockpit, run a 20' vent line out the transom. I've thought of sending copies of my book to all of 'em, but if they'd even bother to read any of it, they wouldn't change a thing if it adds even one penny to their costs.

Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein

 

[timb]

thanks for the help. I have 5 of them on the way .they say there good for 3/8 thickness .I'm guessing it's thinner than that just going by it looks like a poor quality tank . is there any sealant needed ? and what should I have on hand to glue a fitting in if it's too thick ? 5200 or west system epoxy? what material for the fitting if I have to glue it in?

also running the line to the bow .I think I can get it there now but after I replace a rotten bulkhead it will not be accessible unless it put in a small door . I may try to put a second vent in the port side .what grade of hose do I need it should never have any waste in it?

 

[HeadMistress]

As long as you're doing this, if you think the tank is poor quality, why not replace it too?

As for sealant, you shouldn't need any if the Uniseal is the right fit for the hole and hole is perfectly round. Any fitting in a Unseal should also seal without any sealant. Use a little dish washing liquid to lube both the Uniseals and the fittings to insert them.

As for the bulkhead...are you sure it's structural? If not, don't replace it...if it is, adopt something similar to what home renovators do when they want to remove a load bearing wall to open up a room (you'll prob'ly want to get some advice from someone who knows how to do that...I've seen it done, but doing it is above my pay grade). Otherwise install a door in it big enough to make it possible to replace hoses and/or clear a clogged vent as needed.

You can use Shields or Trident #148 flex PVC for a vent line. You shouldn't need a second one.

 

[Woodland Hills]

To determine where to drill a hole through the boat I tape a rare earth magnet on the inside where I think would be a good location. Then take another rare earth magnet outside and see where it sticks. If that location looks good, then I remove the magnets and drill the hole.

This is a very good idea with many possible applications! Thanks for a great tip!

 

[stubones99]

Finally, a boat with a urinal!

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...

The first boat I've ever seen (other than cruise ship) that has a urinal! Only one, and it's in a "downstairs" head off the master. It has the master stateroom in on the galley / salon level, but the head is forward, down where the V berth would be.

At least it has a urinal.

https://www.yachtworld.com/boats/2008/cheoy-lee-bravo-3251503

It has a skylounge, but no nav station there (odd).
The nav station is above the galley, and below the skylounge...

The wrought Ironwork used for hand rails and such get in the way with the original and functional hand rails.

Apparently the boat took a lightning strike so everything but the hull is new or nearly new.