Black Water Pump Out Dilemma

For years, I've read the black water tank threads with a "lucky that's not me" mentality. Well, it looks like my turn has finally come.

Following Peggie's advice, I'm getting ready to ditch my black water vent filter and enlarge the hose including a nice mushroom through-hull fitting so my tank can breathe and I can ensure the vent is clear. In preparation, I went to the pump-out dock to empty my black water tank.

My black water tank is full (don't ask me how I know...it's not pretty). Nothing would pump out. What I tried:

Yes, the pump-out is working (at least it is vigorously sucking up seawater).

No, the vent is not clogged (well, it may have been but I disconnected it where it attaches at the top of the tank so there was no blockage before pumping).

Thinking the pump out line was plugged by solids at the entrance to the tank, I ran a plumbing snake down the deck fitting and "stirred things up."

Took it back to the pump out and still got nothing.

The kicker, I took the boat out (where it is legal) and the diaphragm pump allowed me to empty my tank overboard with no issues.

What in the world is going on here?

This may seem overly simple but did you uncoil all of the hose from the pump-out? We have to uncoil all of it from the stand and lay it on the dock for it to function properly.

Good thought. We obviously think alike. Yes, it was all laid out straight.

A valve?

You might check the dock pump out is really working by using a bucket of water as a test to see if it will pump the bucket empty. KISS, keep it simple. Try the easy things first.

Last pumpout I did had a heck of a time getting the hose end to seal on the deck fitting. I blame it on being cold weather. Hose is fitted with a tapered rubber end. Had to really press on the handle to seal.
Thinking of getting one of the fittings that screws into the deck fitting and attaches to the hose end with a solid connection.

Solly said:

Last pumpout I did had a heck of a time getting the hose end to seal on the deck fitting. I blame it on being cold weather. Hose is fitted with a tapered rubber end. Had to really press on the handle to seal.
Thinking of getting one of the fittings that screws into the deck fitting and attaches to the hose end with a solid connection.

Click to expand...

Simple way to seal the rubber fitting to the deck fitting is to run a small amount of water from a hose onto the fitting. Then the pump will suck in water instead of air and it will pump well. Just don’t use the potable water hose...

Dave,

I didn't try that but I did stick the hose in the water, watched the seawater immediately pull up into the clear sight glass in the hose, and felt the hose get heavier when filling with water so I'm pretty sure the suction is working. I'll try the bucket trick next time I'm at the dock to be certain.


Bayview, although it's been about a year, I've successfully pumped out before and there have been no changes to any valves or plumbing. I'll trace the plumbing when I get down there just to be certain.

Well if the pumpout is working and the vent hose is unhooked and the pumpout hose is clear, then you have me stumped. And you were able to dump it at sea. This is strange. Maybe send Peggie Hall, The Head Mistress, a PM and ask her, she is the guru of all things head related.

Thanks Dave,

I'll probably do just that. It's really got me scratching my head...

Our pump out had a small crack around the connection near the pump out end. I had to work hard to get enough of a seal to work. Put it over the side and it pumps sea water like crazy. I had to hold it just right and push down on it just right. Finally it was recently fixed.

No need to send me a PM...


You pulled the vent line off the tank...did you scrape out the vent fitting on the tank? If not, it's possible you were able to dump the tank because the suction created by the diaphragm pump is a lot less than the suction from the pump out...that your vent may be allowing enough air to be pulled in for it to work, but not enough to keep up with the demand from the pumpout. When you try to pump out, are you hearing any hissing sound from the toilet? Did you hear any when you dumped the tank?



Are you hearing any hissing sound from the deck pumpout fitting? That could indicate it's just not sealing tightly.


If none of the above, the pumpout equipment may be the culprit. Can you try pumping out at another marina?


--Peggie

An air leak in the circuit to the deck pumpout fitting will prevent a pumpout. It could be anywhere between the fitting and the tank.

Ken

Ken, you just raised a possibility that hadn't occurred to me. Any air leak in the tank discharge plumbing would have to be between any y-valve and the deck fitting. He wouldn't be able to dump the tank if it were between the y-valve and the overboard discharge pump. Or, if instead of a single discharge line with a y-valve in it, he has TWO discharge lines--one dedicated to the deck fitting, the other dedicated to the overboard pump, any air leak would have to be in the line to the deck fitting.

Which raises the question: how old are the hoses? 10 years is average working life of any hose 'cuz rubber and plastics dry out over time, becoming hard, brittle and prone to cracking and splitting. If his are even close to that age, you may have found the problem.

--Peggie

There is another possibility. Overboard pumps usually draw from a fitting at the bottom of the tank. Deck pump outs often go to a fitting at the top of the tank and a tube extends down to the bottom. If this tube has become detached you woul be sucking air straight from the vent and never get any effluent.

Just a side note, last season I too finally decided to follow Peggy's advice and delete the vent line filter, and replaced the screened-over vent cap outside the hull with a new, bigger one. I was very skeptical and expected significant stink rising from the new vent cap. Vent line filter manufacturers make millions selling charcoal-filled, space age, whiz bang filters, how could they be useless or a bad idea? And Mainship even designed the holding tank plumbing and fittings and mounted a dedicated bracket to include a filter, how could Mainship be so wrong? And I probably spent hundreds over the years replacing those stinking filters (literally stinking) every year and every time they got wet, so I was financially invested in the whole vent line filter concept. Well what do you know, it worked -- Peggy was right.

Peggie (and others), Thanks so much for the input.

I didn't hear a leak at the deck fitting but there certainly could. be a leak further down the line. It's all accessible so I'll have to try again with someone up top and me in the lazarette listening to the hose. This is where one of those locking hose ends would come in handy.

I didn't scrape the vent input and it is relatively small (probably 1/2" hose) so that could be plugged. I'll check.

As far as leaking hoses, I've had the boat for 5 years now so they are at least that old. It also looks as if the PO painted them when they painted the bilge. There is no sewage smell in the bilge/lazarette and I don't know if the hot towel trick would work as they are painted.

I do have two discharge lines, both of which are at the bottom of the tank so there's no doubt they're in the "stuff."

The only thing I neglected to mention is the hose from the tank to the deck pump out has a Y fitting (not a valve) with one side going to the deck fitting and the other side going to a manual Whale gulper type pump for emptying the black water tank. That manual pump is never used, especially since the handle is blocked by my fuel filter. Would it be possible for the vacuum to be going through the whale pump instead of from the tank?

When you get the tank empty, if it were my boat I would replace all the hose to and from the holding tank. If you have had it 5 years and who knows when the PO changed the hoses, then they are most likely at end of life. I think the best hose is Raritan SaniFlex. The best price I have found is at Defender. No affiliation.

A different direction solve the problem. Introduces other concerns ("litter box" to steel Peggie's thunder) but certainly solves a lot of issues OP is experiencing.

https://natureshead.net/

I would say that whale gulper is probably the weak link. Is there a shut off vale before or after it? if not then if one of the Gulper's internal valves go bad you have an air leak through the pump. If the diagram develops a leak you have a leak also.

Duvie, No shut off valve. I'm going to try to plug the through-hull for that pump (it's about 6" above the waterline) to see if there's any suction there.

Dave, thanks for the recommendation. I'll see how much I need.

kthoennes said:

Just a side note, last season I too finally decided to follow Peggy's advice and delete the vent line filter Vent line filter...manufacturers make millions selling charcoal-filled, space age, whiz bang filters, how could they be useless or a bad idea?

Click to expand...

I've said many times that I only wish I could have put a product on the market that actually helps to create the very problem it's sold to solve.

Why would Mainship even go so far as installing brackets for filters? I've also said many times that boat builders are the WORST sanitation system designers on the planet because they can't be bothered to learn that that they ARE systems and treat 'em as if they're no different from fuel and water systems, when in fact--unlike fuel and water--sewage has to be MANAGED. (I'll climb down off my soapbox now.)

All that said...there are situations--a large tank buried in the bowels of the bilge requiring vent lines that have to follow such a convoluted path that even aeration can't work--that make a filter necessary. But those are very rare. 99% of the time a bit of plumbing and venting modification will make filters unnecessary.

--Peggie

You've made two contradictory statements:
I do have two discharge lines, both of which are at the bottom of the tank so there's no doubt they're in the "stuff."

And
The only thing I neglected to mention is the hose from the tank to the deck pump out has a Y fitting (not a valve) with one side going to the deck fitting and the other side going to a manual Whale gulper type pump for emptying the black water tank.


"Two discharge lines" means two entirely separate lines coming out of the tank--one going directly to the deck pumpout fitting, the other going directly to the overboard discharge pump. So what you actually have is one discharge line that's split by a Y or a TEE fitting.

To answer your question Would it be possible for the vacuum to be going through the whale pump instead of from the tank?


No. A pump--pumpout or overboard discharge pump--will try to pull in air from wherever it can. That should be through the vent, but if it can't get enough air through the vent it'll try to pull in air from any place it can...which is why I asked if you hear any hissing in the toilet during pumpout attempts. That's one of the first clues that a vent is blocked.


And btw...it's unlikely the hot rag test will work on hoses that have been painted. That a PO painted 'em is a very good indication that he was trying to block odor from 'em.


--Peggie

Sorry I wasn't clear.

I have two discharge lines -
Line 1 - goes to the electric diaphragm pump for at-sea pumpouts (this one works).

Line 2 - goes up to a Y fitting (no valve) with one side going to the deck fitting and the other side going to a manual diaphragm pump for manual at-sea pumpouts. This is the pumpout that is not working.

Since the deck fitting is on the same discharge line as the manual diaphragm pump, my question was could the vacuum be pulling through the manual diaphragm pump instead of out of the tank (only possible in my mind since they're on the same leg and feeding one of the discharge lines).

Hope this clarifies my question/situation.

You're probably right about the painting of the hoses.

Yes, I would get rid of the manual pump or cap it and see what happens. If you get it pumped out then I would get rid of the Y valve and manual pump.

Line 2 - goes up to a Y fitting (no valve) with one side going to the deck fitting and the other side going to a manual diaphragm pump for manual at-sea pumpouts. This is the pumpout that is not working.

I'm not surprised! Who's idea was it to have TWO discharge pumps on two separate lines??? I'm 99% certain that if you get rid of the manual diaphragm pump (or just convert it to an emergency bilge pump completely removed from your sanitation system) and wye fitting and run a new uninterrupted line from the tank to the deck pumpout fitting, your pumpout problem will be solved. And I wouldn't be surprised if you find a buildup of waste in that line--most likely in or at the wye fitting that clogged it.

--Peggie

I had that problem on my boat a while back. It turned out that the vacuum from the pump out was causing my gated wye that directs waste to the tank or overboard to close. Now I secure the valve in the proper position and it pumps out fine.

Cheers, Bill

I installed 2 vents, both 1.5" and the front one was around the front by the bow and the rear one was at the wide part of the hull. My thoughts were that the air would be forced to circulate through the tank underway and life would be good. That proved to be true, but while being anchored, the ambient wind did exactly what I had designed it to do, but the smell was a nuisance. I now have a single 1.5" vent.

Bustlebomb

Same boat - similar problem.

short story:
emptied the tank / lots of bleach
replaced the hoses from the tank to all the various in/outs/pumps etc.
the hose is not cheap either. works like a champ even with biggest of guests on board
----------------------------------------

what i found was the hoses at the lowest areas/turns had whatever residual seawater and who knows what else created a concrete/scale substance that lined the interior of the hose walls and lots & lots of the scale in broken pieces/chunks inside that could "possibly" bunch up under heavy suction causing a clog.

If you can disconnect the tanks discharge line below the Y (above it goes to the deck fitting and pump out) and look inside it at the turn up from the bilge - have a container ready and whack it a few times and see if there is heavily scaled/concrete with barely an opening and other substances - start there and if it is - good luck.

The fact that your macerator worked adds to the mystery. On my 411, there is only 1 discharge hose coming off the tank. there is a Y in the engine room where it goes to the pump out fitting on the deck and to the macerator. Kicker is you have to shut the outgoing valve on the macerator side to get suction out of the deck fitting (learned that the hard way). If yours is similar, if the macerator works, the pump out side should work as well.
Got to love being a boat owner. Keeps you thinking all the time.