Vented Loop

[MaryEllaRose]

I‘m in the process of replacing the sanitation hoses on my ‘90 Catalina 25 and have discovered that there was no vented loop on the toilet discharge line. These the original hoses. There is a slight uphill run from the toilet to the entry point on the top of the holding tank but the tank and the toilet are pretty much on the same level. Should I include when I replace the hoses? There’s not much room to add one and keep it significantly higher than the top of the tank.

 

[dlochner]

No need for a vented loop, although a high loop would be helpful in preventing back flow from the tank if the boat is heeling. High means high enough that the contents in the hose will drain back into the tank.

Vented loops are necessary for overboard discharge to prevent siphoning and they go after the pump. When pumping water through the loop event closes due to the pressure. When pressure is relieved due to the pump stopping, the van opens and breaks the vacuum preventing a siphon from forming and flooding the boat.

 

[Peggie Hall HeadMistress]

No need for a vented loop, although a high loop would be helpful in preventing back flow from the tank if the boat is heeling. High means high enough that the contents in the hose will drain back into the tank.

It only needs to be a few inches higher than the top of the tank and has the added advantage of makiing it necessary to pump long enough to push bowl contents over the top of the loop...gravity will get it the rest of the way to the tank.

A vented loop in the toilet intake IS necessary. It does not go in the intake line between the thru-hull and pump, it goes between the pump and the bowl and needs to be at least 6-8" above the boat's waterline at ANY angle of heel, not just when the boat's at rest. That puts it 2-3
FEET above the bowl on most sailboats. This will require replacing the short piece of hose the toilet mfr used to connect them with two sections of hose long enough to do this.
--Peggie

 

[MaryEllaRose]

We flush the toilet with fresh water from a dedicated tank. Do I still need the vented loop between the pump and the toilet?

 

[nabalab]

Is a discharge vented loop required when the holding tank is located higher than the head?

 

[Peggie Hall HeadMistress]

No...a vented loop in a discharge line is only needed in a line connected to a below-waterline thru-hull.
However, depending upon how far above the toilet the tank is, there may be other discharge plumbing issues to deal with. What's the make/model/approx age of your toilet? How high (in feet) above its discharge fitting is the inlet fitting on the tank? Is it on the top of the tank or at the top of a vertical "wall?" Is the tank directly above the toilet? If not, how far away (in feet) is it? And, not that it matters here...what size is the tank?

As for whether you need one in the intake (it would go between the pump and the bowl, not in the line from your flush water tank to the pump)...that would depend on the location of your flush water tank...higher, lower or on the same level as the toilet. Intake vented loops are intended to prevent water OUTSIDE the boat (or in your case water in your flush water tank) from seeking its own level INSIDE the boat by overflowing the toilet bowl. The make/model/approx age of your toilet also has some impact on whether a vented loop is needed.

--Peggie

 

[nabalab]

Peggy:

Thanks for getting back to me.

We are using a Raritan Marine Elegance toilet that is flushed with fresh water from fresh water holding tanks or city water when docked. All of the parts within the toilet, including the marine discharge motor/pump assembly, bowl throat adapter, joker valves, etc. have been replaced with brand new. The only original part is the china bowl. We also have installed brand new 1 1/2" Raritan sani/flex sanitation hose. We are venting the holding tank also with the Raritan 1 1/2" hose. The holding tank is 40 gallons (TK432), 3/8" thick. Holding tank is brand new too. Holding tank is 16" wide, 23" deep and 28" high. Bottom of holding tank is located about 15" higher than the toilet location. Thus, top of holding tank is 43" higher than toilet. The waste line discharge fitting is located at the top of the holding tank. Vent fitting and fill fitting are also at top of the holding tank. Holding tank is located about 2' from toilet. Waste line hose from toilet to top of holding tank will be about 8' long. Vent line hose is straight shot out and is about 12'" long. Pump out hose is about 15"

We did the forward head in the same manner and all is working well. We did install a discharge vented loop in the forward head, which now I know was most likely not necessary.

Your book (How to Get Rid of Boat Odors) is EXCELLENT! We have relied upon it in redoing the sanitation.

I most likely will be asking for further advice in the near future on our fresh water lines.

Happy Thanksgiving!

 

[Peggie Hall HeadMistress]

Thanks for the kind words! But I'm not the right person to ask about fresh water plumbing...I only do one thing--sanitation systems--and it's all I can do to keep doing that very well! However, there are knowledgeable boat owners here who can give you excellent advice.

--Peggie