Hard to pump out black tank

Tried to suck out the holding tank yesterday and it took forever to get a good flow.

I had to repeatedly release then provide suction. Also put some fresh water down deck drain and that seemed to get it going.

Any ideas? Could a vent be clogged? If so how does one unclog a holding tank vent?

cardude01 said:

...Any ideas? Could a vent be clogged? If so how does one unclog a holding tank vent?

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Yes, your vent is clogged. Check the inlet at the hull. Bugs like to make nests there. If that doesn't work, disconnect the vent hose at the tank and look there. I've found some solids from over filling the tank. Blow the hose out with air or use a water hose to clean the vent line. Just remember don't bite your finger nails or using your drinking water hose.

Our marina has cam lock fittings for pump out .The cam locks did not match up very well and we didn't get a good seal . It has always been slow pumping out .We thought at first we had a bad gasket but the fitting didn't match perfect . It took me a while to figure it out but I did . I thought I was the only one having problem but everyone was . This went on for at least a year . I got a big attaboy from our marina mgr and most everyone on the dock . Now pump out is three times as fast

Just replaced our vent hoses with one size up .
You would be surprised how much stuff gets in the vent lines.
Best to flush with water every couple of years Air doesn't seem to work as well.
My buddy disconnects the vent at the tank and puts a hose attachment on it and lets it run for 5 min. Pretty funny to watch the projectile brown stuff come out

Only every couple of YEARS??? The best way to prevent vent line blockages is by sticking a hose nozzle up against the thru-hull and back flushing the vent line into the tank every time you wash the boat and/or pump out. If you have a thru-hull that doesn't allow you to do that, replace the thru-hull with an open "bulkhead" thru-hull. Backflushing regularly will flush out any bugs and clean out any "brown stuff"...and sending it back to the tank doesn't get it all over the side of your boat.

That is...unless you have a vent line filter installed. Those can't get wet. If you have one, that could be where the blockage is.

cardude01 said:

Also put some fresh water down deck drain and that seemed to get it going.

Click to expand...

Did you put the water down the vent line? or just into the black tank.

If just in the black tank then the waste didnt have enough fluid to move.

Good advice above. While you're at it, if you don't have one, get one of the screw in adaptors that SeaLand makes for your waste outlet. Then you can lock the hose fitting onto that for a much better seal than trying to manually seat the pointy ended thimagig into the outlet and have to kneel there pressing and holding it in place.

HeadMistress said:

Only every couple of YEARS??? The best way to prevent vent line blockages is by sticking a hose nozzle up against the thru-hull and back flushing the vent line into the tank every time you wash the boat and/or pump out. If you have a thru-hull that doesn't allow you to do that, replace the thru-hull with an open "bulkhead" thru-hull. Backflushing regularly will flush out any bugs and clean out any "brown stuff"...and sending it back to the tank doesn't get it all over the side of your boat.

That is...unless you have a vent line filter installed. Those can't get wet. If you have one, that could be where the blockage is.

Click to expand...

Ok. Putting the hosepipe on the vent line exit at the stern and blowing it back into the tank is kind of what I was thinking of doing.

caltexflanc said:

Good advice above. While you're at it, if you don't have one, get one of the screw in adaptors that SeaLand makes for your waste outlet. Then you can lock the hose fitting onto that for a much better seal than trying to manually seat the pointy ended thimagig into the outlet and have to kneel there pressing and holding it in place.

Click to expand...

They didn't have threads to fit my waste outlet in the deck so I was using some big rubber thingy. This could have also been part of my problem. Thanks

what_barnacles said:

Did you put the water down the vent line? or just into the black tank.

If just in the black tank then the waste didnt have enough fluid to move.

Click to expand...

Just down the waste outlet on the deck.

Larry M said:

Yes, your vent is clogged. Check the inlet at the hull. Bugs like to make nests there. If that doesn't work, disconnect the vent hose at the tank and look there. I've found some solids from over filling the tank. Blow the hose out with air or use a water hose to clean the vent line. Just remember don't bite your finger nails or using your drinking water hose.

Click to expand...

Ok. Thanks. Will try to clear that vent.

I also tried to pump out while underway offshore and couldn't get it to pump. The macerator would run for about 10 seconds and shut off. Tried it a few times then quit before I blew something up. Macerator is new.

Just trace the obvious...none of this is hard or rocket science...but is formidable until you understand what pieces and parts are involved. But go through every piece till understood...then it will never stump you again.


The basic diagrams all over the internet on head and holding tank manufacturers or on a site like Raritan's will give you the basic idea of what is necessary for a basic system.


add in a little guidance from experienced boaters or techs and you will figure it out.

Cardude as has been said, it sure sounds like a blocked vent. That would also explain the problem with the macerated pump. When you get a chance pick up a copy of Peggie Hall's book.

Definitely a blocked vent line could cause the pumpout action from either a macerator pump or dockside vacuum pump to stall as the tank vacuum builds from a dropping liquid level..

If you do have a ventline filter then be sure the filter is not the problem.

Even if you have a ventline filter and it is itself not the problem I have backwashed the lines by making a jumper hose that bypasses the ventline filter.

My vents [2] came with a screen installed. They were really fuel vents for gasoline tanks. The screens became fouled/blocked. By making the hose jumper and bypassing the filter I was able to backwash the screen and the hoses successfully. I did not want the filter wetted.

I also had, on another boat, a Jabsco macerator pump goof up. The motor ran but there was no pump out action. I took the pump off and opened it up. The macerator part had come unscrewed from the drive shaft which then allowed the impeller to slip. Resecuring the macerator with some BLUE 242 loctite fixed that problem.

It may not be a blocked vent. It may be, but not necessarily. I had the exact problem and it turned out to be a blocked pickup pipe in the tank. Could not even get water down into the tank through the pumpout fitting. Wound up opening the tank to clear the blockage. When we opened the tank top (removed the plate where the level indicators are mounted) the pumpout boat lowered a hose into the tank and emptied it. We followed that with water into the tank from a hose nozzle aimed at the bottom of the pickup tube. Then we repeatedly tried to force water down the deck pumpout fitting. Eventually it cleared. Good luck.

cardude01 said:

I also tried to pump out while underway offshore and couldn't get it to pump. The macerator would run for about 10 seconds and shut off. Tried it a few times then quit before I blew something up. Macerator is new.

Click to expand...

Next step after you clear the pump out problem is to get rid of that POS macerator and replace it with a Sealand diaphragm pump. You will be very happy you did down the road.

cardude01 said:

I also tried to pump out while underway offshore and couldn't get it to pump. The macerator would run for about 10 seconds and shut off. Tried it a few times then quit before I blew something up. Macerator is new.

Click to expand...

My pump out has y-valve between deck pumpout and macerator for discharge underway . Could there be a y-valve shut off some where ? I still think it sounds like clogged vent.

In the past a deck waste fitting was usually 1 1/4 , today the std. is a 1 1/2 size

This lack of commonality can cause hassles, esp if cam lock fittings are used.

A maceriator pump could be used to pump the waste far enough off shore , but I have found seldom used units may need to be cleaned to operate as they can not suck with any residue on their suction valves.

A gravity feed would be fine , but messy to retrofit on most older boats.

The Dupree RV valve system is great for a retrofit .

Many boats have a far too small vent setup, even if its clear.

The waste boat may have a vacuum tank that is ready , and may collapse the side walls if a modest tank.

The truly independint vessel might switch to a portable hand waste/bilge pump with the proper deck fitting.

The Edson 1 1/2 inch on a board works fine

This would meet the fed+state requirements as the boat would present with NO overboard discharge.
No seacock , locked or not , no Y valve ..

If the time is available the deck wash can be used to refill the waste tank to remove more of the solids, when pumped a second or third time..

KISS

cardude01 said:

Ok. Putting the hosepipe on the vent line exit at the stern and blowing it back into the tank is kind of what I was thinking of doing.

Click to expand...

In order for this to work, you need to have the tank empty and the deck pump out access open. The air/water/blockage that's you're trying to push back into the tank needs a vent/escape. If the tank is sealed your fighting a closed container as you blow back thru the vent line.

cardude01 said:

I also tried to pump out while underway offshore and couldn't get it to pump. The macerator would run for about 10 seconds and shut off. Tried it a few times then quit before I blew something up. Macerator is new.

Click to expand...

Capt.Bill11 said:

Next step after you clear the pump out problem is to get rid of that POS macerator and replace it with a Sealand diaphragm pump. You will be very happy you did down the road.

Click to expand...

How would that be an improvement? And what macerator does he have and why is it a POS?

-Chris

Capt.Bill11 said:

Next step after you clear the pump out problem is to get rid of that POS macerator and replace it with a Sealand diaphragm pump. You will be very happy you did down the road.

Click to expand...

Come to think of it mine is a diaphragm pump not a macerator pump . It makes sense , waste should already macerated from toilet before heading to tank .

The problem I have is I never get a chance to check out this side of my waste system because it's illegal to discharge waste underway here . I have to keep y-valve locked off . I know systems always work best when used on regular basis . Anyone have an idea how I could legally check this side of my waste system out say once a month or so? If I ever needed it in an emergency I would like to know that it works .

Larry M said:

In order for this to work, you need to have the tank empty and the deck pump out access open. The air/water/blockage that's you're trying to push back into the tank needs a vent/escape. If the tank is sealed your fighting a closed container as you blow back thru the vent line.

Click to expand...

Ever notice that a pumpout can always remove at least a gallon before the pump pulls a vacuum? Unless you're trying to fill up a tank via the vent line, there's enough air space in the tank for the quart or so of water in a blast from a hose to make it through the line to the tank. Remember, this is PREVENTIVE maintenance, not the cure for a blocked vent.

Before you blast water through the vent line, be sure you don't have a charcoal filter inline.

Pack Mule said:

The problem I have is I never get a chance to check out this side of my waste system because it's illegal to discharge waste underway here . I have to keep y-valve locked off . I know systems always work best when used on regular basis . Anyone have an idea how I could legally check this side of my waste system out say once a month or so? If I ever needed it in an emergency I would like to know that it works .

Click to expand...

If you ever bothered to rinse out your holding tank (which should be done 2-3 x year, and especially in preparation for winter or other extended layup to clear out any sludge), there's nothing illegal about filling a tank half full of clean water and dumping it through the macerator pump...which should be done as part of rinsing out the system anyway.

However, since you can't use it, I'd remove it....it's not that hard to put a new one in if you're ever in waters where you can use it....and testing it every month or so--which we both know would turn into MAYBE once a year--won't keep any machinery in reliable working condition. Besides, there is no holding tank or toilet "emergency" on an inland lake or river that can't be met with a bucket till you can get to a pumpout facility...which you'd prob'ly have to use anyway because that's when the pump would decide not to work.

HeadMistress said:

If you ever bothered to rinse out your holding tank (which should be done 2-3 x year, and especially in preparation for winter or other extended layup to clear out any sludge), there's nothing illegal about filling a tank half full of clean water and dumping it through the macerator pump...which should be done as part of rinsing out the system anyway.

However, since you can't use it, I'd remove it....it's not that hard to put a new one in if you're ever in waters where you can use it....and testing it every month or so--which we both know would turn into MAYBE once a year--won't keep any machinery in reliable working condition. Besides, there is no holding tank or toilet "emergency" on an inland lake or river that can't be met with a bucket till you can get to a pumpout facility...which you'd prob'ly have to use anyway because that's when the pump would decide not to work.

Click to expand...

I rinse out tank several times a year but just thru the pump out station . I think I would have a hard time convincing the TWRA officers here that I was discharging clean water from my holding tank. Removing the system would be best . Thanks Peggy

Most boats have either a surface mount or recessed mount vent with screens, like the picture. When they plug, and they always plug, I just take a 1/8" drill bit and drill the shiny stainless face of the unit. Too small for most bugs, big enough for air.

That looks exactly like what I have on the stern.

I don't understand where you are drilling them out.

So far, my monthly pump-out guy hasn't mentioned a problem. (I'm keeping fingers crossed.) He leaves a small packet of white crystals to be flushed down the toilet.