how much of waste should pumpout remove?

[er9]

I pay to have someone come by and pumpout my holding tank. Today was his first visit, tank was full. I noticed that the tank is still 1/3 to 1/2 full after his visit. Should he have emptied it all the way to the outflowtube level on the bottom of tank or is it normal for some amount to be left over? Never did this before so not sure what to expect.

[transmitterdan]

I assume he charges by the tank and not by some volume amount like gallons or liters. In any event one would think the standard practice would be to pump out everything they can.

A working pump out system should remove everything down to the level of the pump out fitting near the bottom of the tank. It should suck air back through the vent line and the air should come out the pump out deck fitting. That way they know it is "empty". There will be some amount left but not 1/2 or 1/3 of a tank. I would politely ask him to come back and finish the job. Let us know what happens.

[peghall]

Pumpout should empty the tank to the top of the discharge fitting, at which point the pumpout starts sucking air and can't get any more. That typically leaves only about an inch in the tank. If he couldn't get more than a few gallons, it most likely means that the tank vent is blocked.

The tank vent has two main functions: 1. to provide an escape for air displaced by incoming contents. When no air can escape, the system becomes pressurized. 2. to provide a source of air to replace contents as they're pulled out by a pumout or overboard discharge pump. If no air can be pulled in, it causes the pump to pull a vacuum that prevents it from pulling any more out after the amount of air above the surface is exhausted. It sounds like that's what's going on in your system.

The two most common locations for a vent blockage are the vent thru-hull and the vent line connection to the tank--both that end of the vent line and the vent fitting on the tank. Use a screwdriver blade, ice pick or whatever works to scrape out the thru-hull...then try pumping out again, keeping a very careful eye on the pumpout sight glass to make sure anything is being pulled out. If not, you'll also have to clean out the other end of the vent line. Open the deck pumpout cap very carefully to relieve any pressure before removing any hose from the tank.

If you're new at all this, you might want to check out the link in my signature...it goes to a comprehensive "marine toilets and holding tanks 101" manual that can prevent a lot of "head aches."
Peggie
"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
http://www.amazon.com/New-Get-Rid-Bo...dp/1892399784/

[Jd1]

You might have a plugged vent, you might have an inaccurate gauge if it is electric/electronic or you might have a solid pile in there if the black tank sat for a few years full of s&*^.

It is very obvious when the tank is pumped when everything pumpable has been removed. I would look at the gauge first of all unless you can directly sight the tank level.

[er9]

Originally Posted by transmitterdan

I assume he charges by the tank and not by some volume amount like gallons or liters. In any event one would think the standard practice would be to pump out everything they can.

A working pump out system should remove everything down to the level of the pump out fitting near the bottom of the tank. It should suck air back through the vent line and the air should come out the pump out deck fitting. That way they know it is "empty". There will be some amount left but not 1/2 or 1/3 of a tank. I would politely ask him to come back and finish the job. Let us know what happens.

They charge me for a 40 gal holding tank. It was full so he sucked out at least 20 gallons before stopping for whatever reason.

[er9]

Originally Posted by peghall

Pumpout should empty the tank to the top of the discharge fitting, at which point the pumpout starts ......../

Thanks peggy. I know the vent line it not blocked. Its possible the vent thruhull is but itlooks pretty clean. I will try forcing air through it tomorrow.

He actually did empty this tank once before (same guy). it was full of water from the previous owner. He came by and I forgot to switch the diverter valve. He never actually pumped out anything because of that and never said anything. When I looked through the clear plexi cover it was still full of water. He did come back the next day when I realized my error and successfully removed the water. My guess is the vent is ok. I recently replaced every hose in the system and diverter valves.

My neighbor recomended I go over to the local fuel dock. They will pump out for $5 that way I can see it done and verify there is a problem before I can the pump out guy.

[er9]

Originally Posted by Jd1

You might have a plugged vent, you might have an inaccurate gauge if it is electric/electronic or you might have a solid pile in there if the black tank sat for a few years full of s&*^.

It is very obvious when the tank is pumped when everything pumpable has been removed. I would look at the gauge first of all unless you can directly sight the tank level.

No gauge...there isa clear plexi window on top oftank so I can look inside. The p.o. had filled the tank with fresh water, aluminum tank. It was very clean except there was some aluminum slime on the bottom. Hard to say how much so it is possible it clogged a line. I would be surprised though it didnt look that bad.

[hamburking]

I have found the pump out fitting on the tank is either on the bottom, or on the side as low as possible. Knowing which side the fitting is on would allow me to heel the boat over to get as much out as possible. I had one boat with a flexible "bag" tank, that I would lift and slosh the last little bits out.

Also, after "most" everything is out, its common around here to send a few buckets of water down the head and suck some more, and repeat a few time if there's no one waiting in line behind you. This way you might be left with just a little water in the tank, maybe a litre.

Not all pumpouts are created equal. Some can suck a golf ball through a garden hose...others can barely get the flow going. I like the ones with a clear section of hose, so you can SEE whats going on...or rather, coming out.

[Dave22q]

It might be a vent issue but my bet is on a rushed pump out operator. If he tries again and you are still 1/4 or more full I would fill with hot water and laundry detergent just before the next try. If it is dried crud the hot soapy water might break it loose. I doubt a blocked vent because he did pump more than half the tank. Also you might pump the toilet when he is pumping out. That should break any pressure buildup. On the other hand, checking both ends of the vent hose is not difficult.

[buzzstar]

Should you not ask the pump out person? I does not sound as if he is voluntarily forthcoming about things. Some people are just that way.

[PaulinOz]

The pump out system is based on a vacuum pump lifting the product out of your tank into his tank. The only force acting on the black water to lift it is atmospheric pressure ie: 14.7 PSI.

A perfect 100% vacuum will lift distilled water approx 30 feet at sea level
A perfect 100% vacuum will lift mercury approx 30 inches at sea level.
What you are sucking out will be somewhere in between these to levels.

The amount of lift is based on the vacuum generated in the hose connected to your deck fitting. This will be effected by the pumps performance and possibility of air leaks in the connection line to the boat and the deck fitting connection seal.

The vacuum level can be greatly effected by very small air leaks in the system. eg: bad o-ring on connection fitting.

Your tank should be emptied to the bottom.
It may not be any thing to do with your boat or tank system.

[BruceS]

I get pumped out weekly and the best way to know if he gets the lot is to watch the suction hose. When it starts jumping & bucking I know it's starting to suck air. I've asked him to let it continue for a bit after that happens. I also stand out the back to ensure that end is lower than the front.

[Island Time O25]

+1 on watching the see through portion of the hose. Our pump outs are mobile and have pretty powerful suction mechanisms so under pumping is never an issue.

Is your filler screw cap connected to the filler fixture with a little ball chain or some such? If so this tether if thick enough may be preventing the complete suction vacuum from forming, especially if the suction cup is old and not too flexible. Though I am not very versed in these things technically and may be it would not in any case.

[Twidget]

On my boat the holding tanks are above and behind the heads. There is a 2' flex hose from the bottom of the tank to the overboard discharge valve. We are in the Chesapeake Bay and the overboard discharge valves are sealed shut (with wire ties) as the bay is a "No Discharge Zone". Do I need to worry about the sewage settling out and getting hard in the hose and valve?

I know some people "rinse there tanks" out. That just doesn't seem legal to me.

[ranger58sb]

Originally Posted by Twidget

On my boat the holding tanks are above and behind the heads. There is a 2' flex hose from the bottom of the tank to the overboard discharge valve. We are in the Chesapeake Bay and the overboard discharge valves are sealed shut (with wire ties) as the bay is a "No Discharge Zone". Do I need to worry about the sewage settling out and getting hard in the hose and valve?

I know some people "rinse there tanks" out. That just doesn't seem legal to me.

ALL of the Chesapeake Bay is NOT a No Discharge Zone (NDZ). OTOH, being inland means you can only discharge TREATED waste (see Raritan PuraSan, ElectroScan, etc.), where allowed... which is most of the Bay.

The area around Herring Bay is an NDZ. Can't discharge TREATED waste there.

There are products to use in holding tanks, and would usually have at least some effect on waste on the bottom of your tank and on remaining waste in your overboard discharge hose. Research posts by Peggie Hall (Headmistress) and others for products like Noflex, KO, Odorlos, etc.

-Chris