New head install from scratch.

[GWB]

Peggy - have you changed your mind about the loop? It is necessary?

If there was someone smarter than me around they could work out at what depth below the waterline the force of the water overcomes the suction of the pump and flows up the line while the pump is drawing.. thus overcoming the atmospheric force of gravity pushing down. My head is about 2 feet below the waterline.

Did you say that number is 33 foot Stu?

 

[Peggie Hall HeadMistress]

No...I haven't changed my mind...

Peggy - have you changed your mind about the loop? It is necessary?

I dunno how many different ways I can answer the same question...

In my very first reply I said, " You CAN install a vented loop in the head intake between the pump and the bowl...but you really don't one this time."

Later I said, "It's hard to go wrong erring on the side of caution...I would never try to talk anyone out of installing any safety device. And while a vented loop is usually not needed if the toilet intake is teed into the head sink drain, your boat could be an exception. So if you're more comfortable with one installed, then by all means install one."

Its become VERY obvious that, whether you need it or not, you're never gonna be comfortable without it, so install it!!

I keep specifying that it be located between the pump and the bowl because that's where it has to go in ANY below-waterline installation. Teeing your head intake line into the sink drain line does NOT change that.

 

[GWB]

Thank you.
In my mind one should be installed because if the selector on the Raritan was left in wet mode there is a chance the bowl would overflow. That would not happen with a vented loop between the pump and the bowl

 

[Stu Jackson]

Atmospheric pressure pushes down

Did you say that number is 33 foot Stu?

No, please read what I did say. 33 feet of head which equals 14.7 psi, that is the pressure pushing down from the atmosphere.

You may want to do some Wikipedia on basic hydrodynamics, 'cuz it sure isn't working from my explanations to you here, sorry I can't be more clear.

But if that isn't enough, just try this:

you are sucking on two input tubes; one has air and one has water.

Which one is easier to pull on?

Ever snorkel?

And it has nothing to do with how far below the waterline your pump is.

BTW, this has nothing to do with vented loops.

We recognize that not everyone was good at science in high school.

Why not just try it, instead of debating it here?

Bring your plug. Again: please.

 

[Peggie Hall HeadMistress]

Oh yes, it can!

Thank you.
In my mind one should be installed because if the selector on the Raritan was left in wet mode there is a chance the bowl would overflow. That would not happen with a vented loop between the pump and the bowl

One more time:

A vented loop cannot prevent "ram water" (water forced up a hose through an open thru-hull when the boat is underway) from flooding and overflowing a toilet or turning a sink into a fountain. So you'll still have to close thru-hulls and make sure your guests remember to leave the toilet in the dry mode.

 

[GWB]

Yes - I get it that ram water could cause an overflow. It is unlikely that there will be ram water when the boat is not moving, thus the loop is for when someone forgets to close the supply line and leaves the boat.

Stu - your snorkel analogy is no good because there is only the tube going up to the surface. Now if there was another hole at the bend in the snorkel what would happen?

FWIW - I do accept what you say is correct Stu, but I'm curious. If the head intake was bigger than the sink drain line it might work.

Why does everyone get so uptight about these things? Isn't the board for discussion about these issues?

See ya!

 

[Stu Jackson]

Uptight? Hardly

FWIW - I do accept what you say is correct Stu, but I'm curious. If the head intake was bigger than the sink drain line it might work.

Why does everyone get so uptight about these things? Isn't the board for discussion about these issues?

What we've been trying to explain to you is what happens in real life. You simply appear to be ignoring reality that we're attempting to explain. I'm sorry that you can't seem to get it, and perhaps my explanation wasn't as good as it could be, but them's the facts. It WILL happen as Peggie and I have been trying to get you to understand.

So, once again, instead of killing the messengers, why not just try it and see what happens? :bang:

Perhaps then you can come back and explain it to US!

And, yet again, your sketch was incredibly good.

 

[Peggie Hall HeadMistress]

Hey Stu...

Wanna borrow my hammer? :dance:

 

[GWB]

What we've been trying to explain to you is what happens in real life. You simply appear to be ignoring reality that we're attempting to explain. I'm sorry that you can't seem to get it, and perhaps my explanation wasn't as good as it could be, but them's the facts. It WILL happen as Peggie and I have been trying to get you to understand.

So, once again, instead of killing the messengers, why not just try it and see what happens? :bang:

Perhaps then you can come back and explain it to US!

And, yet again, your sketch was incredibly good.

Heres an idea - instead of saying "it wont work" have an explanation of WHY it wont work

And I have not killed the messengers - just asked a few polite questions

 

[Peggie Hall HeadMistress]

I'm gonna try to explain it one LAST time...

Heres an idea - instead of saying "it wont work" have an explanation of WHY it wont work

We keep giving you answers, but you don't like 'em...so you ask the same questions over and over again... You're like the guy who asks "what time is it?" but won't accept the answer without being told how a clock works.

When it comes to the plug in the sink, there's no safety issue, so if you want to try flushing the toilet without one, by all means do it! You'll only find out that you need one...'cuz here's what will happen:

The first pump stroke MAY pull any water that's already in the sink drain line into the head intake line...it'll also pull air into the line from the sink. That air will interfere with the toilet pump's ability to prime, same as a vented loop installed between the thru-hull and pump will do...and each time you pump, you'll pull in more more air...you MAY get a little water, but the toilet won't ever prime. Plugging the sink prevents the toilet from pulling in air, allowing the pump to prime...iow, to start a siphon. Removing the plug introduces air into the plumbing, breaking that siphon...the same way the air valve in a vented loop brings air into the plumbing to break the siphon started by priming the pump.

That's all the help I have to offer you. Good luck with your installation. If you have a specific problem with the toilet, contact Raritan tech support at 800-352-560 x 6.

 

[GWB]

Hey - once again thanks for the help

 

[Bill Roosa]

Hydrodynamics (and statics too). I agree with Stu that the air presses down on the water in the sink hose, however it also presses down on the water outside the boat so there is not "net" pressure pushing the water in the sink hose. If there was the water would start moving. I have not noted it ever moving BTW. Now if you apply a suction from a pump then the energy to move the water comes from where? Right, your hand on the pump. that energy travles down the head supply tube as a suction wave (less pressure than atmospheric) till it hits the Tee. It then splits in two and travles up the sink drain and down through the thru hull and out to the sea. All the suction wave does is try to get the water moving so the line with the least amount of water in it will move a) most and b) fastest. From your drawing (you did not indicate "not to scale") it would look (to me) that the water would "prefer" the thru hull route but it is all about the mass of water in each tube after the Tee and some friction effects if the flow rate gets higher. I suspect that the amount of water in the sink drain is less than the amount in the thru hull hose. So I would conclude that the water will lower in the sink to the point that air gets sucked into the pump. Which is what the rest of the folks have been saying. I also suspect that your sink has a stopper, probably came with the sink.

Seems like a silly discussion since it is so easy to just try it both ways.

 

[GWB]

Thanks Bill