Head backfilling underway?

[patrickkidd]

Have any of you had a head back fill with black water from the tank while underway? The tank was relatively empty so this is surprising. Super fun to clean up after a few upwind legs too.

Maybe open or close a valve somewhere to stop suction or something?

Thanks!

 

[thinwater]

New joker valve. probably a clogged vent too. If it is a Jabsco twist lock, use a Rairtan PHII joker valve (interchangeable, lasts longer).

 

[patrickkidd]

I will also add that the black water tank seems to fill up faster and faster, and the vent usually spews waste onto the deck when full. I feel like the pump doesn't really get it all out or something. I've also tried the macerate which runs fine, but it's hard to tell when it's "done."

I emptied it out with the macerate yesterday, and it's already full today with just one head use and some dishes done. Now I'm getting that rushing sound of water in the cent again.

Thoughts?!? This is kind of a major pain!

 

[Peggie Hall HeadMistress]

Have any of you had a head back fill with black water from the tank while underway?

Ok...think about it for a minute: the tank was almost empty...the inlet fitting on the tank is on or at the TOP of the tank. So either you'd have be heeled over far enough to capsize for anything running back into the toilet to be coming from the tank, or the tank isn't nearly as empty as you thought it was. Since you say the tank is filling up a lot faster than it used to, I'm guessing the tank has lot more in it than you think...and that points to a blocked tank vent.

Tank vent 101: ALL tank vents have two main functions: 1. to provide an escape for air in the tank displaced by incoming contents....2. to provide a source of air to replace contents being pulled out. When the vent is blocked, no air can get out, which pressurizes the system...the first clue is increasing back pressure when you pump the toilet. A blocked vent also prevents any air from coming IN the vent, which causes the pump--pumpout or macerator pump--to pull a vacuum that prevents more than a gallon or two from being sucked out.

And that's what seems to be happening to you if you're heeling far enough to send tank contents high enough in the tank to overflow into the head discharge line.

The two most common locations for a vent blockage are the thru-hull--or on most older Catalinas, the holes in the rail stanchion into which Catalina ran the vent line....and the other end of the vent line--that end of the hose and the vent fitting on the tank. Start by cleaning out those holes...use an ice pick. Then--after you've opened the deck pumpout cap to relieve any pressure in the system (I'd be sure to stand UPwind of it and have a hose at the ready), remove the vent line from the tank and scrape out that end of the hose and the tank fitting. That SHOULD solve your immediate problem. To prevent future problems, relocate the vent line to a thru-hull that you'll have to install. Use a plain ol' thru-hull, NOT a "vent" thru-hull, 'cuz a plain ol' open thru-hull will allow you to prevent vent line blockages by sticking a hose nozzle up against it and back flushing the vent line every time you wash the boat.

However, a tank that's half full or more can still run back into the toilet discharge line when you're heeled enough, so to prevent that, you'll also want to put a loop--not necessarily a vented loop, just a loop--in the toilet discharge line that's higher than the top of the tank.

When the run from the toilet to the tank is uphill, anything left in the line can also run back to the toilet even when the boat is at rest because water--and waste--does have this annoying tendency to run downhill. The cure for that is to put the aforementioned loop immediately after the toilet, so you'll only have to pump long enough to push waste over the top of it. Then switch to the dry mode to push anything left in the line between the toilet and the top of the loop over it. And you can because any toilet that's working anywhere close to factory specs can move waste up to 4 feet vertically in the dry mode. (Yes, really!)

As for whether a new joker valve will help or not...it's not the solution to your problem, but if it's been at least a year since it was replaced, replace it. Even a brand new one won't do more than block a flood under pressure, but the joker valve is important to the toilet's efficiency.

 

[patrickkidd]

Excellent reply, thank you. Especially about the loop.

I don't think my cent tube is blocked because when it acts full it pumped waste out the stantion onto the deck. I pulled the vent tube off the thru hull from within the cabin, and it develops good suction and starts pulling through the head when I put my thumb on the vent tube. AI rushed in the tube when I take my thumb off. I'm sure it could use a cleaning but I'm wondering if there is something else causing this immediate problem?

this is the first time I've used a macerater pump, Does it spin freely with no movement out the side of the hull when it's empty? When mine runs it keeps making gargling sounds (like its pumping but not steady like a water pump) as it spins and it appears that clear water is gargling out from under the hull. But I'm wondering if it's pumping air? How can you tell? Also strange is that for a second there it started slowing down and hen eventually stopped, and wouldn't respond when I turned the switch on and off. I then flushed some water into the head to see if the macerate had a liquid-level relay or spent hung and it started doin it's gargling thing again, but pumping way more liquid out than I had just put in.

So I'm wondering how all this is supposed to work...

Thanks!

 

[Peggie Hall HeadMistress]

...this is the first time I've used a macerater pump, Does it spin freely with no movement out the side of the hull when it's empty?

The macerator pump is an impeller pump...running it "dry" (without anything going through the pump) for more than a few seconds will "fry" the edges of the impeller, preventing it from pulling anything through the pump. So if your vent is clear, I suspect your macerator pump needs a new impeller. Because even normal use, gradually wears off the edges of the impeller vanes, impellers should be replaced every couple of years anyway.

Best way to find out whether your vent is allowing the tank to be competely empty is a trip to the marina pumpout--which is the only legal way to empty a tank anywhere in SF Bay--and especially in Richardson Bay, which is the only NDZ on the whole west coast north of Santa Barbara. You'd have to be at least 3 miles on the other side of the Golden Gate bridge to dump a tank legally...so unless you're still in AK in December, you shouldn't be using the macerator pump anyway. If the pumpout doesn't empty your tank to within an inch of the bottom, you have an obstruction somewhere--vent or pumpout line.

 

[patrickkidd]

Great tips all around. I will check on the impeller then.

For future reference, how can you tell when a macerater is done pumping out?

 

[Ralph Johnstone]

For future reference, how can you tell when a macerater is done pumping out?

You will here a sharp increase in the RPM once the pump starts sucking air. Don't let it run for more than a second or two once it's finished as the impeller doesn't like running without water for lubrication.

 

[patrickkidd]

Is it practical to add a fuel-level floater to the black water tank like they have in a lot of RV's?

 

[Ralph Johnstone]

Is it practical to add a fuel-level floater to the black water tank like they have in a lot of RV's?

Unfortunately, the float types have a life expectancy of weeks until they are cleaned .................... again and again and again.

I got sick of it and installed an external sensor type a number of years back.

http://www.ferriellosales.com/

 

[Peggie Hall HeadMistress]

I highly recommend the Profile systems from Ferriello...Practical Sailor rated SCAD's private label version as the best.

 

[patrickkidd]

Peggie, does your book include information on maintaining macerators and black water tanks pertaining to this topic? For example on replacing this impeller without causing more damage or exploding lines, checking vents, troubleshooting, etc?

Thanks!

 

[jonelli]

Sorry if I'm hi-jacking the thread a little, but since some questions came up about the macerator pump, I wanted to jump in. I've always heard the same thing: "never run the macerator pump dry. Even for a second".
When I go to use my macerator pump, I noticed that at some point (I'm assuming when the holding tank is empty) the little bit of water that was still been in the toilet bowl gets sucked out so that's when I run over and shut the pump off. I now use that as my indicator that the tank is empty.

Thinking about what was previously said, should that suction even happen if I have a clear vent hose to the stancion?
I haven't noticed any odd head-pump pressure feedback or anything else that would indicate that the vent is blocked, but I have not checked it. I have noticed however, that after I shut off the macerator pump, that there is still some air suction happening at the toilet for about 60 seconds before it equalizes and stops.

 

[Peggie Hall HeadMistress]

Peggie, does your book include information on maintaining macerators and black water tanks pertaining to this topic? For example on replacing this impeller without causing more damage or exploding lines, checking vents, troubleshooting, etc?
Thanks!

Yes.

 

[Newport Bob]

First - Peggie been following your advice and using your products (KO & CP) thru three boats and many years THANK YOU!
Now - yup I had it happen, on the current, new to me boat at the time, the head got a little hard to pump, but was not full (per the gauge), so a few more flushes before morning.
Called the pump out boat next morning and with it alongside opened the pump out --- two foot gusher of "liquid" on me and onto pump out boat and operator. She said "BYE, I'll have George come by later" ---- clogged vent - pressurized tank. Tsunami

 

[Ralph Johnstone]

there is still some air suction happening at the toilet for about 60 seconds before it equalizes and stops.

99.999% chance your vent is plugged. As a check, expose the top of the tank the next time you pump out and see if the surface is sucked in when the macerator is running.

 

[Peggie Hall HeadMistress]

clogged vent - pressurized tank. Tsunami

Yup!...and the first clue is a toilet that's becoming harder and harder to pump.

Fwiw, I've experienced that tsunami first hand. It was before I'd learned the first thing about what I had no idea at the time would become my life's work....first boat big enough to have a toilet and tank. What happened when I opened the deck pumpout fitting that day has come to be memorialized as "the day Peggie was hit by the blue spew." I went over the side and was into the water fully clothed including brand new Topsiders, RayBans and a more than just decent watch even before the spew had subsided. There were still blue stains in the dock finger long after we'd sold the boat for a bigger one and moved to a larger slip.
It happened 35 years ago, but it's not something you ever forget!

 

[druid]

LOL - If Peggy had $1 for every time she explained how a holding tank should be vented...
I only have one vent on mine (boat came that way) but high on the List of Priorities is a second vent for cross-flow ventilation - that worked SO well on my Catalina 36: thank you Peggy!

druid

 

[patrickkidd]

Well I hope you wrote about it in your book because I just ordered a copy!

 

[patrickkidd]

Just to report back, after inspection it turns out the vent was not blocked, and the tank was just filling up. The backfilling started to happen even when not underway (scary) and I think this may have been because the intake hose for the tank was run a little low on the way to the head.unfortunately there isn't much room to run an elevated loop, so I just pushed it to the top of the settee compartment it is in. I have yet to replace the joker valve but that's on the short list.

So we'll see what happens next time the tank is full...