Sanitation hose layout diagram

[Scott T-Bird]

Ok, after all these years, I'm almost ashamed to say that I'm still confused about a simple layout plan for my sanitation hoses. I understand the basics, I'm just confused about the best placement of the directional y-valve. My system is simple. I discharge directly either to the holding tank, or to the thru-hull. There is no route from the holding tank to the thru hull (no macerater pump). Obviously, I am 99.9% routing to the holding tank. I have no problems with the pump-out hose that leads from the bottom of the holding tank. My discharge into the holding tank is at the top of the tank as is normal. I don't particularly have an odor problem, but I certainly want to eliminate all chance of odor.

So my question is, which side of the vented loop do I place the directional valve? My original layout had the valve between the toilet and the vented loop. The Raritan diagram (instructions from the new PHC - PBA that I just purchased) has the directional valve after the vented loop, so that all discharge (overboard and holding tank) has to go from the toilet over the v-loop before being directed either to the holding tank or overboard.

I'm uneasy about the Raritan diagram because doesn't that mean that holding tank odors are directly exposed and open at the v-loop? If I put the directional y-valve in front of the v-loop (between toilet and loop), then only the overboard discharge has to go over the loop (which is the only hose that needs to be protected by the loop). Discharge from the toilet goes directly to the top of the holding tank. Odors are blocked by the small amount of water that remains in the LBA (just like a normal household condition). I've noted other diagrams that show direct discharge from toilet to holding tank, without passing over vented loop.

If everybody assures me that odors do not escape from the vented loop, then I will accept that it is best. It will also make the placement of the y-valve easier for me. It was a little bit awkward the way they originally placed it. But, I thought that a vented loop is just that ... a vent. I don't want an indoor-mounted vent that releases holding tank odor into the concealed space just under the deck, behind the toilet.

 

[dlochner]

The vented loop for the discharge should go between the Y-valve and the overboard discharge. I can't think of any reason to put it between the holding tank and the Y-valve. Peggie may have a different idea, and if so, I'd would appreciate hearing it.

 

[Peggie Hall HeadMistress]

which side of the vented loop do I place the directional valve? My original layout had the valve between the toilet and the vented loop.

It really doesn't matter.
However, assuming that the loop will be higher than the inlet fitting on the tank...if you put it immediately after the toilet--ahead of the vented loop--it can reduce the number of times you'll have to pump your toilet to move the bowl contents to the tank because you'd only have to pump long enough to push it over the top of the loop...gravity will get it rest of the way. The air valve in the vented loop will prevent any odor from escaping from the toilet discharge line.

Off-the-shelf vented loops prob'ly won't have an air valve...it's an additional bit that threads into the nipple on the top of the loop (you'll see the threads if you look at the nipple) that needs periodic cleaning and occasional replacement. The attached photo shows what I'm describing. Bosworth is one loop mfr who offers them...you should be able to find other sources if you google "vented loop air valve."

--Peggie
"

 

[Ron20324]

I read it differently, but then again, it is 0345 EDT. The OP says "directional valve", so I think he is asking different from the answers given? Unless he means which direction (device) the Y alve send, he may mean a one-way valve? Scott?

 

[Scott T-Bird]

I am talking about a standard y-valve. My only concern was holding tank air backflowing thru the vented loop into the cabin. I have a forespar loop and I was just reading about it a little more in depth. It has the standard duckbill air valve or an optional hose barb air vent. With the hose barb, you run a small diameter hose to a thu-hull for outside air. I suppose that eliminates any chance that holding tank air can backflow into the cabin. With the duckbill, you should be "safe" except that when it eventually gets clogged or stiffens, you can get a small air leak into the cabin. I have the standard duckbill valve and haven't serviced it in 10 years or so ... I think it's time to take a closer look.

In any case, I'm pretty sure Peggie just said that the shortest run over the top into the tank is best. I'll just put the y-valve between the toilet and the vented loop. The v-loop is absolutely the highest point. The y-valve is just a little bit higher than the top of the holding tank.

 

[Peggie Hall HeadMistress]

In any case, I'm pretty sure Peggie just said that the shortest run over the top into the tank is best. I'll just put the y-valve between the toilet and the vented loop. The v-loop is absolutely the highest point. The y-valve is just a little bit higher than the top of the holding tank.

You have it backwards. Put the loop immediately after the toilet. That creates a downhill run through the y-valve to the tank or the thru-hull. Putting the y-valve first just complicates the plumbing unnecessarily.

Never put a hose on the vented loop! It would have to be so small--only 1/4"---that it would quickly become clogged by waste and sea water minerals...turning the loop into an UNvented loop that no longer has any ability to prevent a siphon. But because it eliminates any squirting out the nipple, it becomes and "out of sight/out of mind" problem that's never addressed....which is actually what you've let the 10 yr old air valve in your vented loop become. Air valves also require some maintenance-- cleaning at least annually and replacement every few years, but it's a lot easier to remove and reinsert an air valve than it is to disconnect and re-attach a hose from the loop. If you've never cleaned the 10 yr old valve, it hasn't been able to prevent a siphon for at least 8 years and should have been replaced at least once.

--Peggie

 

[Scott T-Bird]

It really doesn't matter.
However, assuming that the loop will be higher than the inlet fitting on the tank...if you put it immediately after the toilet--ahead of the vented loop--it can reduce the number of times you'll have to pump your toilet to move the bowl contents to the tank because you'd only have to pump long enough to push it over the top of the loop...gravity will get it rest of the way.

Well, now I do need clarification. The statement above is conflicting in itself - if you put the y-valve after the toilet - ahead of the v-loop, as you said, the contents aren't going to go over the v-loop (unless the destination is the thru-hull with the y-valve turned accordingly). And the statement in your latest post about putting the y-valve after the v-loop seems to conflict with your statement above. Basically, as long as the v-loop does not release tank odors, I agree with what you said above that it really doesn't matter, except that it is best to make a shorter run to the holding tank to conserve water. Keep in mind that the y-valve is above the top of the holding tank and the v-loop is the highest point in the system. I only have to pump to the y-valve before the contents run by gravity to the holding tank. Is there a problem when the boat heels? In that case, when heeled to starboard, the top of the tank could theoretically be even with the y-valve and contents might back-up thru the y-valve (when it's turned the right way) back to the toilet, but it would have to be pretty extreme - like completely laid over on her beam. The holding tank is just to starboard of the centerline, so it is on the same side as toilet, y-valve and v-loop. Bottom of holding tank is by far the lowest point in the system.

The placement of the y-valve either before or after the v-loop does not complicate the plumbing. It's basically the same either way. The y-valve is right underneath the v-loop. By diverting at the y-valve directly to the holding tank, the run is a much shorter hill and a more direct run to the tank, which is what I thought would be your objective. As far as I can tell, there is no reason to pump the contents to a taller hill (the v-loop), only to be diverted after the v-loop. Isn't it correct that there is no reason for contents that are destined for the holding tank to first go over a v-loop? The v-loop is only necessary for contents that are destined for the thru-hull, right? The hose lengths are the same, either way. Isn't the objective to make the lowest, shortest run to the holding tank to conserve water?

 

[Scott T-Bird]

Never put a hose on the vented loop! It would have to be so small--only 1/4"---that it would quickly become clogged by waste and sea water minerals...turning the loop into an UNvented loop that no longer has any ability to prevent a siphon. If you've never cleaned the 10 yr old valve, it hasn't been able to prevent a siphon for at least 8 years and should have been replaced at least once.

--Peggie

I didn't make this up! Forespar makes an optional vent that fits at the top of the v-loop for venting to a thru-hull, They advertise it. They say that it replaces the standard duckbill vent. Why would the hose have to be such a small diameter? I think the hose barb is actually larger ... I'm guessing 1/2"

Like I said before, I have the standard vent. I brought it home today. I'll take a look and see what condition the valve is in.

 

[Peggie Hall HeadMistress]

The statement above is conflicting in itself - if you put the y-valve after the toilet - ahead of the v-loop, as you said...

Ooops...a typo. This sentence "However, assuming that the loop will be higher than the inlet fitting on the tank...if you put it immediately after the toilet--ahead of the vented loop... should have read "if you put it immediately after the toilet, ahead of the Y-VALVE..."

Sorry for the confusion.

Forespar makes an optional vent that fits at the top of the v-loop for venting to a thru-hull, They advertise it

I couldn't find it on the Forspar site....Do you have a link for it?

--Peggie

 

[Scott T-Bird]

I think I'll try this again with drawings of Option A and Option B. Option A shows the y-valve following the V-Loop, as is the suggested preference. Option B shows the y-valve in advance of the V-loop. Diagrams that I have seen that show a direct discharge from toilet to holding tank don't show a V-loop at all. I'm thinking that the V-loop is only necessary for the hose connections to a thru-hull. If that's the case, then why wouldn't Option B be the preferred installation? I'm looking for the preference between A and B and the reason why! This is all based on the specific layout on my boat as accurately as I can show it. The waterline is indeed just below the rim of the toilet. The top of holding tank is just below the waterline. The pointy end is the bow, all plumbing is on the starboard side, though the tank and thru hull are close to centerline.

The blue highlighted route shows the normal condition when the y-valve is set for discharge to the holding tank.

Attached is the link from Defender for the Forespar vented loop. But you are right about the size and I didn't notice it before … it is 1/4" hose barb for venting outside the hull.

Forespar Vented Loop

Vented loops are a vital component in any onboard plumbing system. Without them, the risk of flooding or sinking is greatly increased because water can be back siphoned into your boat from the outside. Back siphoning can occur through any onboard tank, en

www.defender.com

 

[dlochner]

@Scott T-Bird The drawings certainly clarify your questions. We have option B on Second Star.

Shouldn't the liquid in the holding tank be brown, not blue? Don't want to confuse it with the freshwater tank.

 

[Peggie Hall HeadMistress]

Diagrams that I have seen that show a direct discharge from toilet to holding tank don't show a V-loop at all. I'm thinking that the V-loop is only necessary for the hose connections to a thru-hull. If that's the case, then why wouldn't Option B be the preferred installation? I'm looking for the preference between A and B and the reason why!

Putting the loop immediately after the toilet whether toilet also flushes overboard or not can be very helpful if a)the run to the tank is even slightly uphill...or b) longer than about 6', has bends in it, or both...'cuz the loop will be higher than the top of the tank so you'd only have to flush long enough to push the bowl contents over the top of the loop...gravity will get it the rest of the way. It only needs to be a VENTED loop if the toilet flushes overboard.
You really seem to want to put loop after the y-valve unless you're given a good reason to put it before the y-valve....why? My reasons for putting it immediately after the toilet notwithstanding, wouldn't it be a lot more accessible there?

--Peggie

 

[Scott T-Bird]

Shouldn't the liquid in the holding tank be brown, not blue? Don't want to confuse it with the freshwater tank.

You've never seen blue toilet water dye?

 

[Scott T-Bird]

Another point of reference. All of the labeling on the y-valve has the writing right-side up when installed according to Option B. If I install it according to Option A, all the labeling will be upside down.

 

[Scott T-Bird]

My reasons for putting it immediately after the toilet notwithstanding, wouldn't it be a lot more accessible there?

--Peggie

The y-valve was actually mounted underneath the door into the cabinet, and it was awkward there and too low, I think. I intend to move it to a position underneath the v-loop against the hull (facing me when I open the doors) where I can see it clearly and it will actually be easier to route the hoses, I think. I have to make a mounting block but it shouldn't be difficult.

 

[Ron20324]

Shouldn't the liquid in the holding tank be brown, not blue?

It's a THRONE for crying out loud. It SHOULD be ROYAL BLUE !