Vacuum Pump maintenance

[wingless]

The second thing I would try, prior to opening a sealed system full of human waste, is to utilize a pump out station to clear the lines and the vacuum pump.

My thought is that the holding tank vent fitting would be plugged, the tank would be filled, at least 3/4 full and the pump out station would be used to create a vacuum through to the head. The holding tank isn't designed to resist a vacuum so it should be full to prevent collapse.

The fresh water would be de-energized and de-pressurized, to prevent overflow at the head.

With vacuum at the pump out fitting, the head would be flushed and that vacuum would act on the entire system. It might be required to energize the head vacuum pump to get the duckbills going, so they don't obstruct flow.

The intent is to purge the lines and the pump, from the head to the pump.

Assuming that works, I would flush the line from the head to the pump w/ water from a garden hose so when the sealed system is opened it wouldn't be so disgusting.

Then the tank vent would be restored.

 

[CJ Martin]

If the duckbills and ball seal don't fix it, here's something else to consider.

The head is held to the deck by T-bolts. On our boat, one of the T-bolts had broken, causing a vaccum leak at the base of the head. If your pump is still cycling after changing the duckbills AND the bowl is holding water, you might want to check your T-bolts. It's a fairly straightforward fix.

-CJ

 

[Four Suns]

I would not recommend that anyone try an unproven concept of trying to use a marina's pump out system to introduce a vacuum in a primary holding tank. That has the potential to damage the marina's pump as there is nothing regulating how much vacuum you are applying. Too much vacuum will damage one-way check valves. Additionally, damage to the boat's macerator duckbills can occur as you'll be applying a vacuum on the wrong side of them.. Along with damage to the holding tank and fittings which are NOT designed to see ANY vacuum. That is bad advice.

I will also comment again on some of the "solutions" that are introduced from time to time... some of these things like using a plunger to free duckbills and flushing ice down the toilet are usually not a permanent solution at best and can do damage at worst.

Here's a picture of one of my vacuum tanks in my 480 DB I labeled up:

You'll note that when the "stuff" comes from the toilet, it is dropped in the top of the vacuum tank. The vacuum in this tank sucks it in. This thing is essentially a mini holding tank and you'll notice there is a few inches of fluid that stays at the bottom. If you put ice in this thing, or have a tampon flushed, it goes into this tank and floats.

The fluid is removed by the drip tube (on the left) and is plumbed to the bottom of the tank. The fluid is pulled up the drip tube by the action of the bellows going up and down (basically like a toilet plunger) and two duckbill valves on each side of it. It keeps sucking the fluid out and pushing it to the holding tank. When enough vacuum is created, the motor turns off. Note this: The pump does NOT remove all the fluid and then turn off but leaves fluid in the bottom and turns off when enough vacuum is reached.

So... if you follow the flow, you can see how ice will not make it to the main holding tank from the vacuum tank. You can also see that having a large item flushed down the toilet, especially if it floats, may not make it to the duckbills but may clog up the bottom of the drip tube. Pushing a plunger on the toilet may clear up an obstruction from the toilet to the vacuum tank but it is not going to do jack squat pushing stuff up a drip tube and through the duckbills. In fact, the bellows pump is essentially a built in toilet plunger. If there is something wedged in the duckbills, air will come from the main holding tank back through the duckbills and drain the drip tube so it only has air in it as the bellows pumps away... and it will never create a vacuum... and a plunger on the toilet is not going to move any volume of fluid up that drip tube to make a difference.

If you get a tampon or other big items down the toilet, because the clearance from the bottom of the drip tube to the bottom of the tank is not all that much, you will have to pull the tank out and clean it out. I know... I had someone flush a whole box of tampons down a toilet once. They never made it to the duckbills.

Dental floss is the worst. It floats. It sinks. It goes up the drip tube. It embeds in the bellows. It sticks in the duckbills. All while getting a "special coating".

So.. before I would try a "speculation" on how to fix these things and risk doing all kinds of damage, I would try and understand how they work and consult the manuals on removing blockages or worn rubber duckbills. These systems are pretty simple and, as I have said before, I prefer to change the parts that will wear out on my schedule and not on a "4 people have just gone #2 and it doesn't work" schedule.

My 2 cents.

 

[osd9]

...:grin:

 

[Turtlesboat]

That's nasty.

 

[Four Suns]

That's the coating Sea Ray sprays on all the electrical connections... it's not what you think.

Actually, it's my copyright notice.

 

[Turtlesboat]

Mine seems to be missing that special Sea Ray Grease. Where's chelepop

 

[Four Suns]

They only used it on the yachts.

 

[Four Suns]

I guess I should have used the picture of the port side unit... "looks" cleaner...

 

[wingless]

Perhaps this feedback driven by a proclivity for immersion in human waste. Perhaps it is based on an incomplete understanding of fluid dynamics. It doesn’t really matter.

Thanks for the annotated image. That is very handy.

BTW, on both your holding tanks the fitting from the head to the vacuum tank is not fully seated.

Pushing a plunger on the toilet may clear up an obstruction from the toilet to the vacuum tank but it is not going to do jack squat pushing stuff up a drip tube and through the duckbills.

This is wrong. The pulsating vacuum / pressure from a plunger at the head will act upon the entire system up to the vented holding tank. It will act on the line to the vacuum tank, it will act on the drip tube, it will act on the duck bill valves, it will act on the bellows pump and it will act on the line to the holding tank.

That entire un-vented loop, from the head to the holding tank will be pulsated by a plunger and it WILL move fluid up and down the drip tube. It has to. When a positive pressure is created from the head to the vacuum tank, then that differential pressure also acts on the fluid in the drip tube exerting force on that fluid.

Too much vacuum will damage one-way check valves.

How? A vacuum applied in the correct direction, the direction of flow, would have no impact on the duck bill valve. That vacuum would cause the valves to open, just like normal operation, ‘cepting it’s being pulled instead of pushed.

Additionally, damage to the boat's macerator duckbills can occur as you'll be applying a vacuum on the wrong side of them.

This is another example of an incomplete understanding of fluid dynamics.

The macerator loop terminates at the hull seacock. The closed seacock seals off that loop preventing any reverse pressure from affecting those components.

A vacuum applied to that closed stub has a negligible effect.

Along with damage to the holding tank and fittings which are NOT designed to see ANY vacuum.

My instructions were to fill the tank. What force differences exist on the holding tank when full and vented to atmosphere versus when full of liquid with a vacuum applied? None.

That has the potential to damage the marina's pump as there is nothing regulating how much vacuum you are applying.

Wrong. The amount of vacuum from the marina vacuum pump and from the head vacuum pump are limited by design. In both cases when they pump against a plugged line, such as shutting off the lever valve at the pump out hose deck plate fitting, they will self-limit at some elevated vacuum.

That's the coating Sea Ray sprays on all the electrical connections... it's not what you think.

Actually, it's my copyright notice.

It is your choice to select from any of the poops, in this case diarrhea, for your image signature watermark.

The factory also made liberal usage of Cosmolene on electrical connections, bronze fittings and fasteners on my vessel.

So.. before I would try a speculation on how to fix these things and risk doing all kinds of damage, I would try and understand how they work and consult the manuals on removing blockages or worn rubber duckbills.

That is a very noncommittal RTM for someone faced with a failed head system full of human waste.

What does the manual say to fix this problem? Split the sealed system, clean out the crud and replace the parts? If so and if that is what you advocate, then you and all those following your tutelage, should please satisfy my request to relish in your misery by posting images to save multiple kilowords.

On the other hand, my first solution, to use a plunger, worked for me. No fuss, no muss and fast too.

My second solution, to plug the vent, fill the tank, depressurize the water, open the head drain and create a vacuum to purge the lines from the head should work. There is fuss but it is reasonably clean. I would try this before splitting a line full of human waste, but maybe that’s just me.

 

[Four Suns]

I could go through your snappy little answers one by one but I guess I'll go brush up on fluid dynamics (did I spell that right?) first. You are right that some marina pump outs can be shut off but I know of one down the river at Sunset Marina in Hampton that can't be or it breaks the pump. It has no "off" valve at the handle like newer pumps. Depends on the age/model...

But... by all means... speculate away.

Oh yeah... by the way... the only way you could get a vacuum in the main holding tank is to remove the liquid from it (a pump out removes fluid from the bottom and not air from the top)... then it's not 3/4 full anymore... So when it's 1/2 full of fluid and 1/2 full of air, does it implode then? Or when it is 1/4 full of fluid and 3/4 of air? What limit is the tank designed to hold a vacuum in the upper portion? 1/2? 1/3? 3/4? That 3' x 5' flat area on top of the holding tank that has no reinforcement should do real well with a vaccum on one side... shouldn't it? I don't know much about fluid dynamics. Does it matter that the manufacturer of the holding tank warns about not having a vacuum in the main holding tank? Some of the newer pump outs like the ones in Maryland are based on a big vacuum tank and can pump out my 80 gallon tank in 2 minutes or less. Now you suggest to plug the vent and see what happens? You've got to be kidding! Those super pump out stations are known to implode a tank with the vents OPEN. Doesn't really mater though as the advice being posted is someone's "theory" and not based on practical experience. We'll let the reader decide I guess on what to believe.

A few other tidbits... The volume of air from the plunger would have to be greater than the compression of the air as well as the volume of fluid being pushed up the drip tube. Unless you have a 1+ gallon plunger, no fluid will get to the duckbills if the drip tube is filled with air from leaking duckbills. The drip tube has more volume than a typical plunger. But I'm not a fluid dynamics person. Also, the duckbill-based discharge pump has a single duckbill on each side of the bellows and not a dual duckbill and is not designed to hold a vacuum.

(You should re read my post)

 

[wingless]

(You should re read my post)

Great suggestion, but it still has the same errors.

Now you suggest to plug the vent and see what happens?

Maybe you should read mine, where I state “open the head drain”.

the only way you could get a vacuum in the main holding tank is to remove the liquid from it (a pump out removes fluid from the bottom and not air from the top)... then it's not 3/4 full anymore... So when it's 1/2 full of fluid and 1/2 full of air, does it implode then? Or when it is 1/4 full of fluid and 3/4 of air? What limit is the tank designed to hold a vacuum in the upper portion? 1/2? 1/3? 3/4? That 3' x 5' flat area on top of the holding tank that has no reinforcement should do real well with a vaccum on one side... shouldn't it?

Reading isn’t your strong point is it?

This is my initial recommendation, “My thought is that the holding tank vent fitting would be plugged, the tank would be filled, at least 3/4 full and the pump out station would be used to create a vacuum through to the head. The holding tank isn't designed to resist a vacuum so it should be full to prevent collapse.” What does at least 3/4 full mean? My thought is it encompasses full to 3/4 full, not 1/4, not 1/3 not 1/2 not below 3/4. Sorry that wasn’t clear.

The volume of air from the plunger would have to be greater than the compression of the air as well as the volume of fluid being pushed up the drip tube. Unless you have a 1+ gallon plunger, no fluid will get to the duckbills if the drip tube is filled with air from leaking duckbills. The drip tube has more volume than a typical plunger. But I'm not a fluid dynamics person.

Really?

So the compression stroke on a plunger at the head on a failed system won’t exert force on the fluid in the drip tube? And the suction stroke on a head plunger won’t exert force within the drip tube?

By all means, listen to the person who’s been flush with feces multiple times instead of using your head.

 

[Turtlesboat]

What if you have a tampon applicator stuck in a duck bill valve?

Don't ask me how I know the answer to this question.

 

[Four Suns]

What if you have a tampon applicator stuck in a duck bill valve?

Don't ask me how I know the answer to this question.

You should use a plunger with ice cubes.

 

[Turtlesboat]

Bzzzt. Wrong. infraction for you.

 

[Four Suns]

I believe there is a one infraction per thread limit.

Let me try again...

Hook a shop vac up to the pump out nozzle?

 

[Turtlesboat]

bzzt wrong, no soup for you.

 

[Turtlesboat]

Seriously... even if a tampon, paper towel, whatever... was able to be pushed up through the drip less tube thingy... What's the likely hood that 1) it's going to get through 1 duckbill 2) get past the the bellows (I like to call it the poo masher) 3) get past the second duckbill 4) travel up the hose to the holding tank.

I don't care how big that plunger is, how much suction the pump out hose has. It ain't going to do it.

I've been there, I've got the t-shirt.

You have two options
1) you get the offender to get in there and dig it out
2) you get in there and dig it out.

 

[Hampton]

I don't get the ice cube discussion. Every time I try it, they melt before I can deficate them. Even if I could deficate ice cubes (like some women I've met), wouldn't they melt in the holding tank?

PS - This is really fun to read. I'm learning a lot and laughing the whole time.

 

[carterchapman]

Perhaps this feedback driven by a proclivity for immersion in human waste. Perhaps it is based on an incomplete understanding of fluid dynamics. It doesn’t really matter.

Hey Wingess,

I'm not sure I'd get into an argument over fluid dynamics with a guy who has a Master's in Aerodynamics specializing in CFD...and that's from another guy with a Master's in Aerodynamics...I'll leave it to you to figure out what CFD is...