Resolved!!! Was: Need help… Update: Reverse P-Trap in the Head Discharge??? Was: Holding Tank Question

[jmain]

I definitely need help on this one.

Ok, so I found the problem on our 96 Marlin. There is an upside-down P-Trap behind the head wall, just below the access port.

It has some kind of nipple or vent or hose or something that is broken or missing at the top.
Here is a full view of the P-Trap.

And, here is a close up of the top. (Yes, that is used toilet paper all over it.)

Does anyone know what in the world it is, what it is supposed to do, or how to fix it?

 

[ElyseM]

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[jmain]

I definitely need help on this one.

Ok, so I found the problem on our 96 Marlin. There is an upside-down P-Trap behind the head wall, just below the access port.
View attachment 24118
It has some kind of nipple or vent or hose or something that is broken or missing at the top.
Here is a full view of the P-Trap.
View attachment 24119
And, here is a close up of the top. (Yes, that is used toilet paper all over it.)
View attachment 24120
Does anyone know what in the world it is, what it is supposed to do, or how to fix it?

Thanks, @ElyseM! I swear I have never seen one of those before.

I am guessing it is NOT supposed to be shooting water out the top, when flushing the head….
I’d post a video, but I am not smart enough to figure out how.

 

[Hookup1]

It's called a vented loop. The vent was hacked - a good one doesn't have a hose clamp on the valve. There is a duckbill valve in the top. It may be clogged "open". It's supposed to let air out but not liquid. The valve is replaceable but this one was hacked. New loops are cheap enough - replace the whole thing. Different sizes - make sure you get the right one.

 

[jmain]

It's called a vented loop. The vent was hacked - a good one doesn't have a hose clamp on the valve. There is a duckbill valve in the top. It may be clogged "open". It's supposed to let air out but not liquid. The valve is replaceable but this one was hacked. New loops are cheap enough - replace the whole thing. Different sizes - make sure you get the right one.

Thanks @Hookup1. Any thoughts on what was clamped on there with the hose clamp? (That was done by the previous owners.)

 

[seasick]

The loop isn't a vent to the outside per se but rather acts as vacuum breaker. When there is lower air pressure in the loop it allows outside air to enter. That stops the system from siphoning sea water back into the holding tank. During normal pumping, it stays closed. If it isn't closed, two things happen; the first as you have seen is leakage of waste water. The second is that the vapors from the waste tank can vent out and cause nasty odors on the boat.

 

[Hookup1]

No idea what they did. maybe broke the cap. Best to just replace the whole assembly. When it comes to CPU's (Crap Processing Unit) you really only want to do things once!

As Seasick said it lets air in but should not let liquid out. My mistake.

 

[seasick]

On the bright side, if your valve is bad and you routinely use waste tank deodorant, you bilge may smell like air freshener

 

[jmain]

Thanks to everyone for their suggestions on this. What I learned is that the piece that I was missing is basically a Studor Vent, just like the ones that are under your sinks at home.
While the part that I was replacing probably cost less than $5, I had no idea what it really was, how it looked, how to describe it, who the manufacturer was, or where to find one.
So, I went to Home Depot, spent $50, and had it done in an hour.
The Studor Vent (top 2” of the contraption) is the important piece and was half the cost. The rest is just building an adapter to get it to attach to the pipe that I couldn’t see and only had access through a 4” access hole.

 

[jmain]

Thanks to everyone for their suggestions on this. What I learned is that the piece that I was missing is basically a Studor Vent, just like the ones that are under your sinks at home.
While the part that I was replacing probably cost less than $5, I had no idea what it really was, how it looked, how to describe it, who the manufacturer was, or where to find one.
So, I went to Home Depot, spent $50, and had it done in an hour.
The Studor Vent (top 2” of the contraption) is the important piece and was half the cost. The rest is just building an adapter to get it to attach to the pipe that I couldn’t see and only had access through a 4” access hole.
View attachment 24169
View attachment 24170

View attachment 24171

And, here is the receipt, in case anyone needs to know the parts. Ignore the shower drain cover at the end, that was a different project.

 

[ROBERTH]

Nice work! Suggest if not already done to secure the top of that part so it does not get flopped around too much in the waves.

 

[SkunkBoat]

You could have replaced the whole thing for less

forespar--marelon-vented-loop-1-1-2-hose-barb-5-h-x-7-w--153965

They come in different sizes

 

[seasick]

I think the original vent was open normally and closed when there is pumping pressure . The valve you got at HD looks like an Air Admittance Valve and it is normally closed but opens when there is a vacuum in your plumbing. I don't think it serves the same purpose.

 

[jmain]

On the bright side, if your valve is bad and you routinely use waste tank deodorant, you bilge may smell like air freshener

@seasick, ha! Well, I do use waste tank deodorant, but apparently not nearly enough. I promise you, the bilge didn’t smell like air freshener! But, it did smell like something else!

 

[jmain]

Nice work! Suggest if not already done to secure the top of that part so it does not get flopped around too much in the waves.

Thanks, @ROBERTH. It did fine this weekend and took a bit of a beating. However, I agree with you. I am going to wire tie it to the rigging tube that you can see in the picture. I just need to get a really long wire tie, because it has to be connected blindly with one hand through the 4” access port.

 

[jmain]

I think the original vent was open normally and closed when there is pumping pressure . The valve you got at HD looks like an Air Admittance Valve and it is normally closed but opens when there is a vacuum in your plumbing. I don't think it serves the same purpose.

@seasick, I did find the entire assembly at my local marine parts store. Although it was the wrong size, I did get to see how it works. It is closed all the time to prevent gas or liquid from getting out, when there is higher pressure inside the hose. In the case of less pressure in the hose, it allows air in, but closes as soon as the pressure equalizes. Said another way, it lets air in, but doesn’t let air or sewage out.
All I can tell you is that we spent the weekend on it in the Everglades, where it was pretty darn warm (probably mid-80°s), and it smelled A LOT better that it has since we got the boat!

 

[jmain]

You could have replaced the whole thing for less

forespar--marelon-vented-loop-1-1-2-hose-barb-5-h-x-7-w--153965

They come in different sizes

@SkunkBoat, thanks for the link. I was able to find one at our local marina parts store. The problem with replacing the whole thing is that you can’t see it at all and can only reach it with one hand. I was doing everything through a 4” access port next to the head. It is completely surrounded by fiberglass on all 6 sides.
For about the same price, I’d still be trying to get the original one out, even if I cut a second access port! I had no idea how to get the hoses on the new one, and rerouting is not a feasible option, because there is nowhere else that you can reroute hoses that large above the waterline. There is just almost zero access to it.

 

[seasick]

@seasick, I did find the entire assembly at my local marine parts store. Although it was the wrong size, I did get to see how it works. It is closed all the time to prevent gas or liquid from getting out, when there is higher pressure inside the hose. In the case of less pressure in the hose, it allows air in, but closes as soon as the pressure equalizes. Said another way, it lets air in, but doesn’t let air or sewage out.
All I can tell you is that we spent the weekend on it in the Everglades, where it was pretty darn warm (probably mid-80°s), and it smelled A LOT better that it has since we got the boat!

So are you saying that you saw the correct part but because it was the wrong size, you bought the AAV at Home Depot?
If so, that valve works differently.
Since it is closed at rest and when under pressure, you shouldn't have the odors but, it weather or not it will prevent siphoning is a different question. I suspect if it doesn't you may experience the holding tank filling up a lot quicker than normal.
One other question; On your test sail, did you use the overboard discharge operation? Yoy also may have an issue using a dockside pumpout station.