1 or 1 1/2 inch Head to Holding Tank Lines?

[Sean5306]

I'm overhauling the sanitation system in my Hunter P42. The original lines running from the old Jabsco toilet to the holding tank are 1 in lines. I understand from reading many forum posts that 1 1/2 in lines are common in sanitation systems. And, the line from the holding tank to the pump-out deck portal is 1 1/2 in. The installation guides of the replacement toilets I'm considering all have allowances for either 1 or 1 1/2 in outlet tubing. The length of the hose run from the toilet to the holding tank is ~8-10 ft. The interior volume of a 1 in ID x 10 ft line is 1.6 gal and that of a 1 1/2 in ID x 10 ft line is 3.7 gal. Since the standard flush volume of the toilets is in the range of 1 gal or less, it seems that using the 1 in line would lead to less sewage being left in the lines. However, 1 1/2 in line seems like it would be less likely to clog even if there is buildup inside the lines. I can fit either size through the boat. Which size tubing is the better choice and why? Thanks in advance for any guidance.

 

[JamesG161]

Since the standard flush volume of the toilets is in the range of 1 gal or less, it seems that using the 1 in line would lead to less sewage being left in the lines.

I have never plugged my 1" so I am not going to make a Marine toilet recommendation.
But...
Pumping Solids ...
using the #1 rule that nothing goes in a Marine toilet except what went through your mouth + minimum marine toilet paper

These are relatively easy moving solids. (no pun intended)

Industrially...
To suspend or move solids you must use high velocity liquid flow.

1" line would have ≈44% higher velocity than 1.5" per stroke.

The Jabsco manual pump is like a "plumber's friend" pump. My thought is to use 1" and water flush a known volume of "no solids" water to clean/clear the 1" line to Hold tank. Plus 1" line has lower volume per foot than 1.5".
On my boat, we need 3 pumps of "post flush" water to clear the 1" line. That is also a good indicator line is clear, if no problems to "post flush".
Jim...

PS: The best way to stop a clog is to post a Sign... You plug it, you clean it!

 

[Finally Free]

Do you have the original electric heads still? If so consider they are maceration so really no solids ever go thru the lines. We have never (knocking on wood here) had a plug in the line. Guest did ball up the maceration blades with a baby wipe once.....

 

[Peggie Hall HeadMistress]

Because the inlet port on the tank is 1.5", I'd go with a 1.5" toilet discharge line If you go with 1", you'll have install a reducing adapter somewhere in the head discharge line. Makes more sense to keep it simple.

 

[Sean5306]

Thanks all!
Good point, JamesG concerning the velocity in 1" vs. 1.5" lines. I hadn't thought of that factor. The macerator on the new toilet is one of the major factors I'm focusing on, so I'm feeling like your "easy movement" comment "feels good".
Peggie, actually I'm replacing the aluminum holding tank too (attachment fittings were corroded - nearly failure). The original Hunter drawing of the tank actually specifies 1" NPT fittings for two ports that connect to the fore and aft toilets (plus the pump out port). I replaced it with the Ronco Plastics marine holding tank equivalent (B562). However, the company I ordered the tank through made a mistake and made one fitting a 1.5" NPT and one fitting a 1" NPT. They were willing to spin on a 1.5" NPT fitting to replace the 1" fitting. I think I'll leave it how it is. I can probably put a 1" tubing to 1.5" NPT fitting elbow on the tank and make it so that line is essentially 1" from the head to tank and no extra threaded joints.
Let me know if anyone feels like I'm making a mistake.

 

[Jalepeno]

Check your volume calculations, 1 us gal = 231 cubic inches.
Area = (radius) squared * 3.14
Volume = area * length
Simple high school math here in Canada

 

[Sean5306]

Check your volume calculations, 1 us gal = 231 cubic inches.
Area = (radius) squared * 3.14
Volume = area * length
Simple high school math here in Canada

Pi*(1"^2) * 10 ft * 12"/ft = 377 cu in / 231 cu in/gal = 1.63 gal
Pi*(1.5"^2) * 10 ft * 12"/ft = 848 cu in / 231 cu in/gal = 3.67 gal
I think I have my math right. However,
Velocity = flow/area
So, for 1 gal of flow (per arbitrary unit of time)
1" line: 231 cu in / 3.14 sq in = 73.5 in
1.5" line: 231 cu in / (3.14 * 1.5^2) sq in = 32.7 in
So, velocity in 1" tube is actually 2.25 times that in 1.5" tube.

 

[thinwater]

^^Nope, you used the diameter instead of the radius. Divide your results by 4x.

An easy reasonableness test is that area of a 1" hose has to be less than 1 square inch (pi/4, in fact).

 

[Sean5306]

Oh, Good catch thinwater (and jalepeno)! I was just on a walk and realized I had made this mistake!
10' of 1" hose is 0.41 gal and 1.5" hose is 0.92 gal.
And the velocity ratio for 1"/1.5" hose is still 2.25x.
I don't think this changes the conclusions any, though. Anyone disagree?

 

[JamesG161]

And the velocity ratio for 1"/1.5" hose is still 2.25x.

If you take the inverse ration of 1:1.5 (2.25x) or 1.5:1 = 0.4444 or my ≈44% increase comment...
So now all 3 of us agree on cross section area. Mark one off for our Trig teachers.

My thought is to use 1" and water flush a known volume of "no solids" water to clean/clear the 1" line to Hold tank. Plus 1" line has lower volume per foot than 1.5".

I didn't comment on your "Volume of hose" comment since I was missing the "hose length" of your new installation.
But, I was trying to help you draw that conclusion by my "post flush" to clear the line of solids, and I was not sure of the head's liquid volume per stroke (here is you time factor or flow rate). From my Jabsco head manual...

When the bowl is empty, Open (

) the Flush Control again, and continue to pump until all waste has either left the boat, or reached the holding tank (allow 7 complete up/down strokes per metre (yard) length of discharge pipework).

They were willing to spin on a 1.5" NPT fitting to replace the 1" fitting.

Industrially...
Going from 1" to 1.5" fitting at the receiving tank is a good thing as long as the expansion is in the Direction of solids flow. In other words, DO NOT CONSTRICT moving solids (think about the movement pun).
A tank nozzle at 1.5" is a very very short length and thus reduces the back pressure (now I have changed the subject).

Let me know if anyone feels like I'm making a mistake.

No mistake!

Last point on your new design... I promise.
http://www.jamestowndistributors.co...+Instructions+for+Jabsco+Manual+Marine+Toilet
See Outlet Piping Option 4. which is how my design is. The sewer gas is back flow reduced by water left in your bowl.
So...
At minimum, my "post flow" purge must clear the top of that seal, so all the stuff is now down hill flow.

If you install that 12" rise, the closer to the head you can get, the minimum "post flow" purge needed.
If you purge the line free of stuff, the least chance of plugging.
Jim...

 

[Peggie Hall HeadMistress]

Fwiw, y'all...Most boat owners don't realize that any manual marine toilet that's working anywhere close to factory spec can move bowl contents up to 4 vertical feet or 6 linear feet in the DRY mode. Learning how to use the dry mode to take advantage of this, using the wet mode to rinse the hose BEHIND the flush instead of with the flush, can increase the number of flushes your tank can hold by 50% or more and prevent clogs.

 

[JamesG161]

Fwiw, y'all...Most boat owners don't realize that any manual marine toilet that's working anywhere close to factory spec can move bowl contents up to 4 vertical feet or 6 linear feet in the DRY mode. Learning how to use the dry mode to take advantage of this, using the wet mode to rinse the hose BEHIND the flush instead of with the flush, can increase the number of flushes your tank can hold by 50% or more and prevent clogs.

This is a great tip. Be sure and put a bit of water in the bowl after the dry flush to seal the sewer gas.
Jim...

 

[Sean5306]

Last point on your new design... I promise.
http://www.jamestowndistributors.co...+Instructions+for+Jabsco+Manual+Marine+Toilet
See Outlet Piping Option 4. which is how my design is. The sewer gas is back flow reduced by water left in your bowl.

Wow, you'd put a vented loop in the head discharge line? I get the purpose: prevent water left in bowl from being siphoned into the holding tank so it can serve the sewer gas seal purpose. I see that Jabsco markets the part you referenced specifically for the waste discharge loop. However, I'm a bit loath to put a fitting with a check valve on the top of it into the head discharge line. It seems like keeping it simple is advisable.
I suppose you'd know if the vent gets clogged because your bowl will siphon. Does it provide a path for smell to leak? I'm spending good money on hoses that aren't permeable. I should intentionally add a vent?
Thanks for the info!

 

[JamesG161]

Wow, you'd put a vented loop in the head discharge line?

Not in my case. As long as the hold tank vent is above the healed boat water line, my line has a "vented loop".

Here is the Option 4 new link...
http://www.xylemflowcontrol.com/files/29090_29120-3000_43000-0905.pdf
My first link was incomplete, missing figure 3. Sorry.
I have no Optional 4 "siphon breaker". The reason that Jabsco part (29015 - 0010) is optional....

A siphon is a dynamic event! (often misunderstood)

As soon as the siphon flow is stopped, no more flow can occur! ..... or until you pump a "full line" of water "over the hill" and lower than the bottom of the head, again.

Take that optional Jabsco part out of the 12" seal loop and you "vent" the loop with air from the bottom of the bowl or the Hold tank vent.

That was the beauty of @Peggie Hall HeadMistress dry pumping tip.
Dry pumping would insure no siphon for sure. Which invoked my follow up...
" to pour back in water to seal sewer gas". Read Jabsco operational tip of flipping back to fill bowl or what I like to do is to pour fresh water from fresh water sink, about 12 oz, to stop sea water bacterial stink between days of non use.

In reality you don't need full 12" to make the sewer gas seal work. Why? The water in the Head will stay in the bowl side, even in pretty high seas, fore and aft movements.
Jim...

PS: Who cares about sewer gas smell in 10 foot seas?

 

[RoyS]

Here is a suggestion. When you have to replace the joker valve about annually you will be faced with a flood of waste water from all of the vertical hose between the toilet outlet and the holding tank inlet. My new untried modification can help. I have placed a shut off valve directly after the toilet waste outlet that should limit the spill to less than a cup full. See attached photo.

 

[Peggie Hall HeadMistress]

This is a great tip. Be sure and put a bit of water in the bowl after the dry flush to seal the sewer gas. Jim...

Not needed...the joker valve blocks any sewer gas that doesn't escape out the tank vent. If you maintain your tank aerobically, there won't BE any noxious gasses.

When you have to replace the joker valve about annually you will be faced with a flood of waste water from all of the vertical hose between the toilet outlet and the holding tank inlet.

There should be very little--and it should be clean water--if you've flushed out the system first and then pushed it over the top of any loops or into the tank using the "dry mode."

As long as the hold tank vent is above the healed boat water line, my line has a "vented loop".

Not true. However, although a LOOP in the toilet discharge line may be a good idea in SOME installations, if the toilet only flushes into the tank, it doesn't have to be a vented loop.

Y'all are waaaaaaaay over-thinking this and arriving at conclusions that seriously over-complicate what's really very simple: plumbing a toilet to a tank.