New head install from scratch.

[GWB]

I'm in the process of installing my head for the first time. The head is a Raritan PHII.
I have 2 through hulls, 1 for waste over board (1.5") and 1 for flush water/ sink drain (3/4")
My question: Is there a way to safely plumb the sink drain into the 3/4" inlet for the head flush water? If I plumb the sink drain into the supply water inlet and have a vented loop for the supply water the pump will suck air from the sink drain. As my head is below the water level I need the vented loop.
Thanks for any help

Edit: I think I see now that the vent goes in the line from the pump to the bowl.

So that solves that I think...

Another question: Can plastic fittings be used for the "t" and barbs at the 3/4" inlet? This is obviously below the waterline

Thanks again

 

[Peggie Hall HeadMistress]

I'm in the process of installing my head for the first time. The head is a Raritan PHII. I have 2 through hulls, 1 for waste over board (1.5") and 1 for flush water/ sink drain (3/4").

You didn't mention a holding tank or treatment device...where are you that you can flush directly overboard?

Absolutely!...And it's very safe....in fact, several boat builders use the same thru-hull for the sink drain and head intake. All you need is a tee or a wye. You CAN install a vented loop in the head intake between the pump and the bowl...but you really don't one this time...'cuz although your head is below waterline, the sink isn't. You'd have to plug the sink to prime the toilet...just removing the plug would break any siphon.

However, when plumbing to flush directly overboard you DO need a vented loop in the discharge line...it needs to be at least 6-8" above waterline at any angle of heel...which on most sailboats puts it about 3' above the toilet.

Yes.

 

[GWB]

Thanks for the reply Peggy -
I do have a holding tank, the head output goes to a 3 way valve, one of the valve outputs go to the overboard discharge (via a vented loop) and the other to the holding tank.
I dont fully understand your answer to the sink/head supply question.
Did you say the vented loop is not neccesary?

 

[Peggie Hall HeadMistress]

Oops...I left out a word...

You CAN install a vented loop in the head intake between the pump and the bowl...but you really don't NEED one this time..

The sink serves the same purpose. You do need to plug the sink to flush the toilet...'cuz the pump will pull air through the sink if you don't. But as soon as you remove the plug, any siphon would be broken.

I'd put the vented loop in the discharge line ahead of the y-valve...helps to prevent backflow of any waste or flush water left in the line and/or any from the tank when heeled enough cause the tank contents to run back into the line to the toilet.

 

[GWB]

Peggy - I have some concerns..
Firstly the toilet pump is below the water line... so the water level will be at the inlet to the pump. My thinking is that water will not have to be sucked UP by the pump therefor plugging the sink drain will not be necessary to get supply water to the pump.

If I do not install a loop between the pump and the bowl then I run the risk of water getting through the pump and flooding the bowl and boat.

 

[Peggie Hall HeadMistress]

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.

However, a vented loop does not make it safe to leave the toilet in the "wet" or "flush" mode when not actually in use, or leave the the thru-hulls open when away from the boat. Nor will a vented loop in ANY installation 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.

As for whether it's necessary to plug the sink to prime the toilet pump...that's not a safety issue...you'll find out whether you need a plug the first time you try to flush the toilet without one. I'd have a plug handy.

 

[GWB]

Peggy - thanks! I'll report back if I needed a plug

 

[Stu Jackson]

Peggy - thanks! I'll report back if I needed a plug

You WILL. It's simple: the water from the thru hull is low. The sink is ABOVE the waterline and the air in the hose between the T fitting and the sink will be drawn in by the head pump before it starts sucking any water.

There's only been about a thousand years of hydro research on this one, plus maybe 50 years of boating with heads with pumps that'd tell ya this.

And Peggie, of course.

Get a plug. Please.

 

[Peggie Hall HeadMistress]

Actually at least 2000 years, Stu...

There's only been about a thousand years of hydro research on this one....

Heron (also referred to as "Hero") of Alexandria--the one in ancient Egypt, not the one in VA--was an engineer/inventor who did amazing things with hydraulics, pneumatics, and gears and pulleys. In fact, he came within a hair's breadth of inventing the steam engine...he succeeded in harnessing the power of steam but just considered it an amusing toy because their were no engines in his day to power with steam or anything else! Start here (and do keep on going to Part 2, 'cuz that's where some the best things he did are in this article):

http://www.mlahanas.de/Greeks/HeronAlexandria.htm

when you have at least an hour to spend, 'cuz I guarantee his inventions will keep you fascinated for at least that long.

 

[GWB]

Are we on the same page here? There is NO loop between the head pump and the inlet through hull. The T is at the through hull.
And the head pump is below the water line

 

[Peggie Hall HeadMistress]

I thought we were...

Are we on the same page here? There is NO loop between the head pump and the inlet through hull.

That's correct...that is NOT where the vented loop belongs . Read your very first post to this discussion again...and also the installation instructions for the toilet again...'cuz you noted in your very first post: "I think I see now that the vent goes in the line from the pump to the bowl. So that solves that I think..."

It does, so I saw no need to comment. I guess I should have.

On the subject of the plug in the sink...you also noted: "If I plumb the sink drain into the supply water inlet and have a vented loop for the supply water the pump will suck air from the sink drain."

Actually that will also happen WITHOUT a vented loop...which is why you need a plug in the sink and why I said you don't really need a vented loop. But if you're more comfortable with vented loop, put it where it belongs: between the pump and the bowl as shown in the toilet instructions. And make sure there's an air valve in it...that's a li'l doodad that threads into the nipple at the top of the loop. It allows air INTO a line to break a siphon, but doesn't allow anything out.

Do NOT substitute a vent line instead (this is one place where I disagree with Raritan's instructions). Without an air valve, any loop in a line through which water is being PUSHED--which is what's happening in the line from the pump to the bowl--will squirt water (or, in a head discharge line, waste) that will very quickly clog a tiny 1/4" vent line...turning a vented loop into an UNvented loop that can no longer break a siphon. Because the vent line has created an "out of sight/out of mind" condition, it never occurs to anyone to check it the loop and clean out the nipple and the tiny li'l hose.

 

[kloudie1]

Awwww dont told me dat, Cher.. All dis time I taught he was from Alexandria LOOZIANA! (In my best Cajun accent)

 

[Stu Jackson]

Are we on the same page here? ...
And the head pump is below the water line

But the sink is not, and somewhere between the thruhull, the T and the sink, there is AIR in that hose. Wish I could draw you a picture.

But given all this, you're certainly free to try it without a plug. Let us know how it works out.

Guess it always feels better when you stop hitting your head against the wall.:dance:

 

[Peggie Hall HeadMistress]

:bang:

I've been here for nearly 13 years now .... It's a bit like repeatedly hitting myself in the head with a hammer 'cuz it feels so good to stop each time.

 

[Stu Jackson]

Peggie, the replacement Hammer's in the mail!

 

[woodster]

Peggie, the replacement Hammer's in the mail!

in cajin that is a MATTOOOO

 

[kloudie1]

Mais Yeah ! an matoe !!

 

[GWB]

Please excuse my failure to understand The attached drawing shows the water supply part. Why will water not flow back up the sink line after water is drawn in by the pump?

 

[Stu Jackson]

Good sketch, wished I coulda done that! Glad you asked and are staying with us. Last thing we want to do is chase you away.

Here's the reason: if you draw a BIG arrow pointing DOWN right above the empty sink, label it: ATMOSPHERIC PRESSURE. It is 14.7 psi or 33 feet of head at sea level.

It's pushing down and the sink hose above the water at the T fitting is empty.

When you start sucking with the head pump, it can either suck the water from the thru hull or through the empty sink drain line. The sink drain line is easier, and it will suck air. Period. Proven. Tried. Been there, done that, and all that.

Unless it's plugged at the sink so air doesn't keep getting sucked into the pump.

There may be some better physicists out there who can explain it in more detail, but them's the basics. Hope we can all learn from the details others can add.

As we've all said, give it a try. But have a plug handy. We know, we've all tried it.

 

[Peggie Hall HeadMistress]

The simple answer:

Forget learning hydrophysics 101...Install the vented loop between the pump and the bowl!