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Old 09-25-2016, 07:27 PM   #1
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black water tank won't pump out

After cruising since last Oct 2015 and having no apparent problems with pump outs. I decided to leave the boat on the Ortega River for winter before heading north next spring. When I pulled into the marina I went first to the fuel dock for a pump out. It had been 3 weeks and two people since the last pump out, I have a large tank. Nothing would pump out. We put a few gallons of fresh water in and pumped out a few gallons of brownish water but nothing else. We tried this a few more times and decided it may be a problem with the pump. They brought down their portable pump. Same thing. They sent a man down to inspect the lines for any blockage and he found nothing. All lines seemed free and clear. After five hours of inspecting the only conclusion arrived at was that the tank has turned to mud and needs to be scooped out. My tank is fiberglass and made into the hull of the boat. There is no way to get into it or see into it to guage the consistency of the contents. There is a cover plate where the tank guage sensors are located. As the inspector explained to me (I did not see this myself as there is not enough room for both of us) the cover plate does not open to the tank itself but to a short channel that leads to the tank. If you remove the cover plate you can't see very much. You can't see into the tank at all but you can judge about how full it is. Anyway the suggestion made to me so far is to cut an access hatch to the tank and bucket it out. I have talked to many boating friends, mechanics and marina owners who I have known and worked with over the years and none have heard of crud hardening in a tank that is being used. Any information would be helpful at this point before we start cutting holes in the boat. It is a Sealand Vacu-Flush system and about six months ago I changed tank treatments from the blue SealandD treatment to the KO Bacterial. Yes I use dissolving TP 90% of what goes down is liquid and macerated. How can it get hard???? Thank you very much for any information.
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Old 09-25-2016, 07:34 PM   #2
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I think this is a question for Headmistress!
I feel for you though...
Bruce
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Old 09-25-2016, 07:52 PM   #3
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I think this is a question for Headmistress!
I feel for you though...
Bruce
Likewise. My only suggestion would be to 1/2 fill the tank with water and maybe some sort of chemical cleaner and take the boat out and through her around to mix the tank contents into a pumpable substance,

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Old 09-25-2016, 08:05 PM   #4
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I only had to read the first few sentences to be 99% certain that the "man they sent down" checked every line but one: the tank vent. I'd bet real money that your problem isn't in the tank, it's a blocked vent.

A tank vent--any tank, fuel, water or waste--has two main functions: it provides an escape for air displaced by incoming contents and provides a source of air to replace contents as they're drawn out.

When no air can escape as new contents are added, the tank can become pressurized. Fortunately your boat sat long enough for any pressure in the tank to dissipate or you'd have been "baptised" by geyser when you opened the deck pumpout cap. When no air can be drawn in as contents are pulled out, the pump will pull a vacuum that will only let a small amount be pumped out before the pumpout or macerator pump pulls a vaccum that prevents it from removing any more. A particularly strong pumpout pulling against a blocked vent can implode a tank.

The most common locations for a holding tank vent blockage are 1) the vent thru-hull, 2)the other end of the vent line--that end of the hose and the vent fitting on the tank...and 3) a filter in the vent line. If you haven't overfilled the tank, causing it to overflow out the vent, we can prob'ly rule out the filter--they only block the vent if they get wet. That also reduces the odds of a blockage anywhere BUT the vent thru-hull. Clean it out with a screw driver blade, ice pick or whatever works. If there's a screen in it, knock it out...screens cause more problems than prevent or solve. That should solve your problem.

If you want to prevent this from happening again, replace the "vent" thru-hull that all boat builders use on every tank vent with an open "bulkhead" or "mushroom" thru-hull that you can put a hose nozzle up against and backflush the vent line every time you wash the boat.

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Old 09-25-2016, 08:13 PM   #5
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Peggie,

Is it possible that the "down tube" has developed a hole (s) and the tank contents only pump down to that point? The OP stated that when they add water only a "few gallons of brownish water" would be removed. Just a thought in addition to the vent line.
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Old 09-25-2016, 09:45 PM   #6
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You may be onto something...but he said it's a large tank, and only two people have been aboard in 3 weeks. So unless they spent a LOT of time in the head, it's unlikely that the tank is close enough to full for a "perforated" diptube to pick up only what's at the top of it. Nor did he mention a diptube...but that doesn't mean there isn't one.

So for now, my money is still on a blocked tank vent. I'm amazed that among all the people inspecting and guessing at what the problem could be, that thought never occurred to a single one of 'em.
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Old 09-26-2016, 02:59 PM   #7
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In motorhomes, some folks end up with the dreaded "PooPyramid". Never thought about it on a boat, figure the motion would help eliminate that sort of thing, provided there's enough water.
So I'd bet ventline as well. If that isn't it, might be worth hitting it with as much hot water as you can muster...

Good luck, and please keep us posted...
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Old 09-26-2016, 03:20 PM   #8
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The "pooh pyramid" is much less likely on a boat because RVs literally dump their tanks out a port in the bottom of tank and rarely add water during pumpout to emulsify the sludge that builds up on the bottom. There's also a lot more sludge in an RV tank than in a marine tank because RV toilets use only enough water to rinse the bowl...as little as a pint or two. Marine toilets use an average of a couple of liters/flush, which help to dissolve solids and TP, resulting in a lot less sludge, and marine tanks are pumped out, taking a lot of the sludge out with the liquefied waste. Any that remains in the tank is spread out across the bottom of it.
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Old 09-26-2016, 03:52 PM   #9
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Thank you so much for the responses. I value your experience and appreciate your help. The vent line was the first thing we checked. We changed the filter. That didn't help so we took out the filter all together and left the lines open. That didn't help either. It maybe could be a plug where the vent line connects to the tank. I tried to feel for some air intake on the open vent line where we took out the filter. While the pump was running I held my hand over the open vent hose and didn't really feel any air intake. When we added 2 gals of water in the tank through the deck pump out, some strong gasses vented out the hose so it appears to be open. The tank is full now so no more water rinses can be added. My next step is to try another pumping station. It could be that the pump at my location is not strong enough. It seems like the next logical step. I really don,t want to cut holes only to find out that wasn't the problem. The boat is only 10 years old. The pick up pipe is fiberglass same as the tank.
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Old 09-26-2016, 04:16 PM   #10
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You'd be amazed by the amount of strong odor that can escape through a hole too small to allow enough air to be pulled in through the vent to prevent a pumpout from pulling a vacuum.

You said it could be a plug in the vent line connection to the tank, but apparently no one has checked to find out even though that's one of the two most common locations for a vent blockage. So I'd do that before going to a different pumpout. Remove the vent line from the tank and check both that end of the vent line AND the vent fitting on the tank for a blockage. After you've cleaned out any blockage in the tank vent fitting, try pumping out with the vent line off the tank.

If that doesn't do it, there's one more thing to try that won't require cutting any holes: Run a rod through the deck pumpout fitting down the pickup tube to clear any blockage in it or anything that's plugged the bottom of it. Despite all warnings not to flush anything but TP, landlubber guests will flush wet wipes and one could have made it through the vacuum pump into the tank. If your pickup tube is cut too flat and is close to the bottom one could have blocked it.
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Old 09-26-2016, 04:21 PM   #11
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What is the height difference between the deck fitting and the tank top?

The adapter between the suction connection and the deck fitting, is it yours or the pump out station's? Does it screw in or is it a cone you wedge in place? I have my own adapter with a good oring for a tight seal. Didn't have great luck with the cone. Air leaks can be a problem.

Check all the hose clamps between the deck fitting and tank for tightness. Is there a Y valve in the system for overboard discharge? Is it completely set to deck pump out? Next time you try the pump out, have some one listen near the hose between the deck fitting and the tank, for air leaks.

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Old 09-26-2016, 04:29 PM   #12
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Teresa,

Peggy hit on the first thing that thought of, the vent. When I was wondering recently on the vent in my boat this summer, I loosely taped some thin plastic (grocery store bag) around the vent opening with masking tape. I then watched it as someone flushed the head. The plastic film ballooned out as the head was flushed telling me the vent was open. You may want to try something similar.

Peggy can tell you for sure, but I am convinced that if a tank isn't rinsed well during a pump out that eventually you can get a sludge build-up in the bottom of the tank. If your vent is clear, this may be a problem. In my current boat, I don't think the prior owner ever flushed the tank when it was pumped out. I always do and found that I was never able to get the tank rinsed as clear as I was used to on my prior boats. I would still get chunks of material even after several rinses. I finally started to use No-flex as a tank treatment, then used Peggy's suggestion of cleaning the tank with laundry detergent. After this, and 4 rinses if the tank, the rinse water getting pumped out of the tank was clear. Since then we have had no problem with head odor as well.

So, if the vent is clear and you really think there is a sludge build up, if it was me, I would start to be very aggressive about flushing that tank. Use No-Flex or similar in the tank and empty the head on a weekly basis. Each time you empty the head fill the tank from the waste discharge opening with fresh water and then pump again. Do this several times each time you empty the holding tank. Eventually, the No-Flex digester and repeated rinsing should start to clear out any sludge at the bottom of the tank saving you the pleasure of cutting inspection ports in your tank.

As usual with anything poop related, check with Peggy before paying any attention to anything I type.
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Old 09-26-2016, 04:42 PM   #13
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If you really want to see into the tank, you can buy a small remote video camera that comes with lights and attaches to a flexible tube. Some have a built in monitor and some connect to a computer via a USB port. Stick it down the pumpout opening and see what you can see.


This will work if the outlet is at the bottom of the tank but it may not work if there's a dip tube. You say there's an opening in the top for a sensor so you could probably insert it there also.


If you can get a water hose down the pumpout fitting and into the tank, running water at full force through the hose might dislodge and dissolve any solid matter so it can be pumped out. Don't use your good potable water hose.


And of course, you could cut an access hole in the top of the tank and use whatever works to loosen any sludge. You can buy covers made for this so buy the cover first and cut the correct sized hole to fit the cover.


I would try the TV camera thing first to make sure there is really sludge in there before doing anything drastic.
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Old 09-26-2016, 05:17 PM   #14
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FWIW, one of the projects I need to do on my current boat is to replace the vent hull fitting with an open mushroom. My vent fitting has a very tiny opening, so much that you can actually hear it whistling when the tank is being pumped out. This makes it all but impossible to back flush. Fortunately, this boats vent is actually accessible unlike my Catalinas have been.
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Old 09-27-2016, 06:37 AM   #15
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Teresa,

You have to think that most waste going into the head is 90 to 95% water. Where did all the liquid go? I seriously doubt that you have any thick waste in your holding tank that needs to be scooped out.

If your holding tank needs to be scooped out, then you have a serious problem with leakage and your bilges would smell like a sewer. The liquid in your holding tank would not evaporate.

In my experience, the suction at various marinas varies considerably. You have either a bad pump out, a bad seal where the pump out nozzle fits to your thru hull, or a blocked vent.

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Old 09-27-2016, 08:24 AM   #16
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Cutting holes in the tank and shoveling it out is really drastic.

I have noticed sludging happens more to tanks that are pumped out and don't use their overboard discharge once and awhile----there is always waste left behind and it just compacts (worse if the boat has a great lift height from tank). Boats on the great loop trip seem to have a lot of problems.

Finish checking all the physical things first; which it sounds like you have done.
Noflex Digestor. Search the web you will find users that had the same problem.

Yes I make it and I also use it on my boat.

Zaal,Noflex Digestor, sewage treatment,Holding Tank Treatment,Septic system treatment,Head treatment,boat holding tank treatment ,holding tank waste treatments,RV holding tank treatments,boat head treatments,RV head treatments,

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Old 09-27-2016, 09:56 AM   #17
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There's a very simple way to deal with sludge that doesn't require anything but water and a little effort: Put 4-6" of water into the tank via the deck pumpout fitting--'cuz that sends it into the tank at the bottom to stir up any sludge and hold it in suspension so it can be pumped out or sucked out by the overboard discharge pump. Doesn't matter whether it's fresh water or salt...if you can easily get outside the "3 mile limit" you can even use a washdown pump to put the water in the tank...after you've added a few inches, just keep the water running while you run the discharge pump. If you have to use a pumpout, repeat until you see only clean water in the pumpout hose sight glass. Last step, run enough FRESH water (sea water can be sticky) through any overboard discharge pump to rinse it and its plumbing out.

This should be done 2-3x/season--and especially in preparation for winter or other extended layup--whether you use any product to deal with sludge or not.
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Old 09-27-2016, 10:01 AM   #18
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Cutting holes in the tank and shoveling it out is really drastic.

I have noticed sludging happens more to tanks that are pumped out and don't use their overboard discharge once and awhile----there is always waste left behind and it just compacts (worse if the boat has a great lift height from tank). Boats on the great loop trip seem to have a lot of problems.

Finish checking all the physical things first; which it sounds like you have done.
Noflex Digestor. Search the web you will find users that had the same problem.

Yes I make it and I also use it on my boat.

It is true that when there is a large rise from the holding tank to pump out fitting that the tank never completely empties. However, many boats here in Puget Sound never use, or don't have, an overboard discharge. We can't legally discharge our holding tanks unless we go into the Juan de Fuca Strait. As such, our overboard discharge has to be secured closed (the USCG checks for this on inspection). Even so, we can keep our tanks clear by rinsing the tank when pumping out.

Now, do you manufacture Noflex Digester? I just started using it this summer because of issues with the tank on my new-to-me boat. So far I have been very impressed.
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Old 09-27-2016, 10:03 AM   #19
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Perhaps not quite legal but in the interest of quickly determining whether the sludge is concrete why not try using the macerator to pump out (a little). If that works then presumably the tank contains liquid not solid. Might even be worth a 3 mile run off shore to do this legally.
Depending on the pump-out pump, we sometimes had a problem with the pump attachment not sealing adequately to the deck pump-out port. Even a marginal loss of vacuum was enough to prevent pump-out. Might want to try a different pump-out station before tearing things apart.
We did also have the blocked vent problem shortly after buying our boat. Seemed the PO had let the tank over-fill and crud blocked the vent. The tank vent exit was a simple 3/8 inch stainless 90 degree elbow and totally inadequate for the job. It was replaced with a 1 inch PVC fitting and larger diameter tubing to the deck.
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Old 09-27-2016, 07:27 PM   #20
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Yes we make it and I developed the product
Had a problem years ago with sludge in the big treatment systems on Ferries, mines, Shell oil islands on and on. I helped with some of the designs and a lot of the tek stuff. Some of them are so closely watched samples are inline and tested every hour, realizing there were too many variables, that's were the Noflex came from.
Sludge is a problem for them because of volumes. I modified over the years for the holding tank and septic tank side to get the smells out and sludge and then got into the retail side . It's really 2 products in one .
I'm a power boater I know what the smells are like and it's a cheap fix.
World wide sales on word of mouth and I get to deal with happy people.
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