Fresh water head

[Pinch]

Additional question

Peggy
Just reviewed complete thread and got answers to most of my questions, thanks to you all. One remaining concern is about the small amount of sea water remaining in the sink drain line, below the tee and above the thru-hull, after a "fresh water" flush? Does that ever amount to enough be a problem if left for, say, a month?

 

[Peggie Hall HeadMistress]

Not a problem

Fresh water from the sink will fill the whole drain line, so any remaining sea water in the line will be too diluted to cause any problems.

 

[Pinch]

Fresh water flush

Fresh water from the sink will fill the whole drain line, so any remaining sea water in the line will be too diluted to cause any problems.

Thanks, Peggy. I'm ready to make the changes this weekend.

 

[Roger Long]

I'm a little late with this but here is how I did it:

http://www.rogerlongboats.com/Strider06work.htm#Tailpiece

the line from the dishwasher fitting at the top goes to a Tee in the head intake line just after the seacock. Works great.

 

[Pinch]

Not enough pull from thru-hull

Thanks, Peggy. I'm ready to make the changes this weekend.

Peggy et al

I've installed the "tee" in my sink drain line and the head pulls fresh water well from the sink basin. However when using the raw water option (with sink stoppered and thru-hull open) I don't have enough "pull" to get any raw water input. The Jabsco head is, admittedly old (2000 model), and I had used fresh-water flushing via the shower hose into the bowl alone for 2+yrs - so I suspect there might have been some damage to the valves from that. Does anyone know of another possible cause ?- or am I just going to have to do the "kit" to replace the valves? Thanks

 

[sailingdog]

You have to plug the sink drain, or it will likely act as a vacuum break.

Peggy et al

I've installed the "tee" in my sink drain line and the head pulls fresh water well from the sink basin. However when using the raw water option (with sink stoppered and thru-hull open) I don't have enough "pull" to get any raw water input. The Jabsco head is, admittedly old (2000 model), and I had used fresh-water flushing via the shower hose into the bowl alone for 2+yrs - so I suspect there might have been some damage to the valves from that. Does anyone know of another possible cause ?- or am I just going to have to do the "kit" to replace the valves? Thanks

 

[Ron20324]

You have to plug the sink drain, or it will likely act as a vacuum break.

Dog, he already said he does that.

 

[sailingdog]

Have you checked to see if the raw water through-hull is clear. Barnacles and such can clog them up to the point where they're blocked completely.

If you do have to re-build the head, I'd highly recommend getting a Raritan PHII or PHC instead of rebuilding the Jabsco.

 

[Peggie Hall HeadMistress]

Pinch, is there a vented loop in your head intake?

If so, where is it located? If it's between the thru-hull and the pump, it's in the wrong place and is the reason you're having trouble pulling in sea water. The cure: move it where it belongs--between the pump and the bowl.

Or...your sink plug isn't plugging tight enough?

Or...dog may be onto something...your thru-hull is blocked, or maybe not completely open.

Whatever it is, something is allowing air into the intake line that's preventing the pump from priming There's nothing wrong with the toilet pump. If there were, you'd have just as much trouble pulling water out of the sink.

 

[Ron20324]

The water from the sink is gravity-fed and may disguise a weak pump.

 

[Peggie Hall HeadMistress]

What??? <LOL>

The water from the sink is in the drain pipe...the toilet pump pulls it out of the drain pipe...so what except the drain pipe is gravity fed???

 

[sailingdog]

Peggie—

He's right, but only if the seacock at the bottom is closed or the through-hull is clogged does the fact that the sink drains via gravity have any effect. If the seacock is open and the through-hull is clear, it should, in theory, drain out of the boat, and provide little or no assistance to the head pump.

The water from the sink is gravity-fed and may disguise a weak pump.

 

[Peggie Hall HeadMistress]

Nope...

Gravity drains the sink...but it doesn't have anything to do with the TOILET pulling in sea water via the sink drain thru-hull.

When a thru-hull is below the waterline, sea water will rise in that line to the waterline. The toilet simply pulls the water out of the line, same as it would if the intake line were connected directly to the thru-hull..the siphon started by priming the toilet pump SHOULD keep the sink drain line filled...removing the plug in the sink, even temporarily breaks the siphon. His problem is, something is preventing the toilet from being able to start the siphon.

When the thru-hull is closed and the sink is filled with water, the drain line fills too. Again, the toilet PULLS water from the drain line. Gravity is what keeps the drain line filled till the sink is empty, but it has nothing to do with supplying water to the toilet. But even if it did, he's only having a problem pulling in SEA water...no problem pulling fresh water out of the sink.

When just lit up a question in my mind: I wonder if he teed into the drain line above the waterline? That would explain it.

 

[sailingdog]

Peggie—

My point is that if he was using the sink to flush the head with fresh water, the fact that the sink is supplying some pressure, due to the height of it, it might mask a weak pump, which is failing to draw in seawater against gravity... especially if the t-connection is above the water line.

 

[Stu Jackson]

From a purely engineering point of view

the sink may be draining by gravity, but what makes it work for the head is the atmospheric pressure that's pushing it down, not gravity.

 

[Ken Juul]

Re head re plumbing

I realize I'm coming in late here. Did the mod years ago, works great. My C34 MKi has 3 thru hulls under the head sink. The original set up had thru hulls for the engine, head intake, combined sink/shower drain. The shower drain connected to a tee just above the thru hull in the sink drain line. I just swapped the head intake and shower drain lines. 5 minutes work no new parts.

 

[Pinch]

Re: Nope...

Gravity drains the sink...but it doesn't have anything to do with the TOILET pulling in sea water via the sink drain thru-hull.

When a thru-hull is below the waterline, sea water will rise in that line to the waterline. The toilet simply pulls the water out of the line, same as it would if the intake line were connected directly to the thru-hull..the siphon started by priming the toilet pump SHOULD keep the sink drain line filled...removing the plug in the sink, even temporarily breaks the siphon. His problem is, something is preventing the toilet from being able to start the siphon.

When the thru-hull is closed and the sink is filled with water, the drain line fills too. Again, the toilet PULLS water from the drain line. Gravity is what keeps the drain line filled till the sink is empty, but it has nothing to do with supplying water to the toilet. But even if it did, he's only having a problem pulling in SEA water...no problem pulling fresh water out of the sink.

When just lit up a question in my mind: I wonder if he teed into the drain line above the waterline? That would explain it.

Peggie:

Thanks to you and others for the comments.

To address several points - yes, the "tee" I installed is likely below water line, as the drain thru-hull is only 2-3 inches below water when stationary. Yes the sink stopper is functioning well. And the thru-hull is confirmed clear.

To attempt to obtain/maintain prime, I have tried the following sequence - filled sink and pumped fresh water into the head; then stoppered sink and opened thru-hull with fresh water stll in drain line. Pump worked well initially but after water in drain line fell below the "tee", I only got a trickle of raw water into the bowl (fill mode). Vigorous pumping kept the raw water barely flowing from bowl inlets into bowl, but not enough to fill bowl (fill mode on). This tells me the pump could not maintain prime nor draw raw water up to and over the "tee". This may be from age of valves or damage from my previous filling bowl from shower hose and with no inlet source.

If you believe the valves are likely "shot", should I replace them with Jabsco's kit (on hand but could be returned) or do the Raritan replacement instead? What would the advantages be VS costs differences?

Thanks,
Pinch

 

[Peggie Hall HeadMistress]

To address several points - yes, the "tee" I installed is likely below water line, as the drain thru-hull is only 2-3 inches below water when stationary. Yes the sink stopper is functioning well. And the thru-hull is confirmed clear.

To attempt to obtain/maintain prime, I have tried the following sequence - filled sink and pumped fresh water into the head; then stoppered sink and opened thru-hull with fresh water stll in drain line. Pump worked well initially but after water in drain line fell below the "tee", I only got a trickle of raw water into the bowl (fill mode). Vigorous pumping kept the raw water barely flowing from bowl inlets into bowl, but not enough to fill bowl (fill mode on). This tells me the pump could not maintain prime nor draw raw water up to and over the "tee". This may be from age of valves or damage from my previous filling bowl from shower hose and with no inlet source.

"When the water in the drain line fell below the tee"...

AHA! That HAS to mean that the tee IS above the waterline. The pump can't maintain prime because air in the line is breaking the siphon.

If the thru-hull is only a couple of inches below waterline, the tee would have to be above waterline unless it's right on top of the thru-hull. But even if it is, if the boat rocks at all, it the thru-hull itself can even be at least partially out of the water some of the time.

I don't THINK there's anything wrong with the toilet (and everyone will tell you that I jump at ANY chance to recommend replacing a Jabsco!)...but if you're determined that the toilet is the problem, then go with the Raritan replacement. It has a much stronger pump that moves twice as much flush water and waste/pump stroke, and is the most durable reliable in its class...top rated in the industry for more than 20 years.

 

[Pinch]

Thanks, Peggie - I'll investigate what other options I have to get a positive below water line source (like the original head inlet thru-hull) that still allows me to use fresh water flushing when required. Perhaps I can route the sink drain there with a "tee" for head inlet.
Pinch

 

[Ron20324]

Thanks, Peggie - I'll investigate what other options I have to get a positive below water line source (like the original head inlet thru-hull) that still allows me to use fresh water flushing when required. Perhaps I can route the sink drain there with a "tee" for head inlet.
Pinch

"Ah-ha!", as Pogo said. "We have met the enemy and he is us." Sounds like the tee in the head line will solve your problems. And mine, when I get to it.