Vacuum Pump maintenance

[Four Suns]

Where did I say that? Again, reading isn’t your strong point, is it?

Here is where you said it:

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.

So many of your posts have been deleted I didn't think I would be able to find it. That statement is total BS. If there is air in the loop (and there will be because the way it is routed on all boats), the duck bills will have lower pressure on one side and air that is capable of expanding on the higher pressure side. Since the discharge pump is NOT designed to hold a vacuum because it only has a SINGLE duckbill on each side of the bellows, you run the risk of inverting the valves.


I think you also characterized me as having an incomplete understanding of fluid dynamics... which is obviously the case... so I apologize for my ignorance.

For example, with my limited knowledge of fluids, I would think having a full holding tank and doing this thing would be the worst way to do it. Assuming you have a complete blockage upstream, for every gallon of water pumped out, the volume in the tank will have to go down by a gallon. If there is air in the tank, for every gallon of water you pump out, the air will expand because it is compressible and so the volume in the tank will not have to go down by the same gallon hence reducing the deformation. I think you are assuming that the hydrostatic pressure (rho*g*h) is going to keep the tank from imploding but that pressure is not all that great compared to the issue of sucking out the water and having the volume go down... For example, in this tank:

it could have been filled with water with no air and the water was sucked out so the tank deformed to adjust to the new water volume. A filled tank of liquid will get damaged faster than one with air as you suck the liquid out.

But that's just from last night's reading...

So the full-tank idea to counter any damage is actually the exact OPPOSITE of what the reality is...

 

[Asureyez]

What a Load of Crap!

The tanks supplied by SR are plastic and are never intended to have a vacuum pulled on them. In fact these tanks have vacuum breaks installed in the top of the tanks to prevent over aggressive pumping collapsing the tank as so illustratively demonstrated by Gary's photos. I have had this happen on my 1996 - 370 and it was a disaster to recover from. :smt100

On my 460, I've been plagued with negative pressure in the tanks, over filling due to mis reporting float signals and odor back up due to faulty vent lines and failing seals in the bellows pump out use to overboard waste. On my 460 the heads get a lot of use, first we boat year round, 2nd, I entertain a lot … 6-12 people frequently and I raft out several times a month with many smaller boats. I make guys from other boats return to their arrival boat or take a swim, but I just never have been able to refuse a bikini clad hottie the use of my head even if she didn’t arrive on my boat. Yes, I personally give individual instructions to all transient female guests on proper head use!:thumbsup: Out of necessity I’ve become all to intimate with the Vacuflush system.:smt101

If you have a plug into the line from the toilet to the vacuum pump, my heart goes out to you. :smt021 You’ll have to try everything you can to clear the line even a snake. However, if you are contemplating air pressure or vacuum disconnect the waste line at both ends before applying a vacuum or air pressure to the hose in the hopes of driving the plug out. This is a very speculative approach at best, but air pressure backing from the pump towards the head has worked for others I know, but I’ve never had to resort to it.

What Chad knows about these Vacuflush Systems:

1.) The way to fix plugged heads to never ever let it happen. Never let anyone into your heads that has not been given a lesson in use of the toilet. I make it clear to every guest, before the engines are fired up, that NOTHING goes in the head for flushing that didn't come out of them or the TP I provide, nothing period finis. :smt018 I make it clear the consequence of their non compliance and threaten to ostracize them publically after DNA tests. :wow: This is a direct eye contact conversation. I keep sign in the head reminding guests of my Crappy Rules. I provide trash receptacles and tiny disposal bags for feminine hygiene products to be wrapped and trashed. The number one all time toilet killer is these “Flushable Towelettes” ladies use as butt wipes and seat wipe downs. These things might be fine for home use but will stop up a Vacuflush every time. Ban these from the head.:smt009

2. The Tank vent should have a anti siphon loop with the loop up and not down. If it is down, the loop will fill with condensation and affluent and plug the line. How do I know this, well the SR assembly technique of “upside down inside out” production often confuses the line workers who are clueless as to what they a building and how it is supposed to work. :smt021 In chasing down my odor problem I traced the vent hoses to behind the cockpit liner, behind the fuel distribution valve manifold to find what … Yes ... inverted vent line loops wire tied in the down loop position and plugged from years of residual build up of salt, crap, dust and stuff. Packed solid, couldn’t get air through it. :smt089 Solution was to cut out the loop, replace with a new line section with proper loops and the smell and negative pressure issues vanished. :smt038

3. Faulty tank level sending units. These sliders are good systems right up and until the tank gets any floating waste in there. Paper products (pulp and other vegetable fibers) build up and actually can form a mat floating in there. Also, if a few of these Towelettes make there they will fould the sending units. The sliders get fouled and stuck in the down empty position and then you are geared for a huge problem of the tank over filling, backing out the vent line and plugging the filter and set the tank up for an EXPLOSION. Happened here my friends, I got to scrub out an ER over this one. :smt100 When it happens the tanks expanded to the point of blowing off the restraining straps blowing off hoses and other thrills. Solution is always follow rule # 1 and then 2X a year open the tank clean and inspect the sliders. I periodically pump out the entire tank and remove any remaining debris in the tank from the inspection port. To perform this job of all jobs I will linger at the pump out station, refill fill my holding tanks with fresh water from the top of the tank inspection port with strong stream of water to break up any floating mass and then insert the pump out hose in to the tank and suck out the remaining debris. (Yes, I clean off the hose after). Next clean the float switch rods and magnets with a scrubbing pad so they slide smoothly. Re assemble. Never let the tank over flow and back up into the filters if you do you will replace the filters at $80 a copy and repeat step # 2 above and spend a lot of quality boating time in the bilge with Lysol and a bucket. :smt089

4. If you have a “Y” valve arrangement to pump waste overboard, the typical 12v bellows pump by Sealand has four components that require periodic service. Two duck bills and two “O-Rings”. Here in the coastal Atlantic we can pump out offshore so our pumps are used a lot. When the O Ring(s) go, the bellows pump will fountain affluent into the bilge and you are back to Lysol and a buck in the ER, . OH Joy of all Joys! :lol: If you are getting odor in your bilge it is highly likley you are experiencing O-Ring failure. To fix it either pay a yard 3-500 bucks or, don rubber gloves and repeat after me. Complete step 3 above, except you may want to consider pumping out through the macerator pump 50 gallons of fresh water to clean out the lines to the pump. Flush outy the bilges to reove any affluent on the ER decks. Remove the hoses (inspect clamps), and unscrew the pump nipples (these unscrew to the right - the wrong way and should be just hand tight) and replace the duck bills ($25 bucks) . Then remove the bellows drive cover and remove the wrist pin on the bellows rod. From the bellows side of the pump remove the retaining clips around the bellows base and the bellows will unsnap from the pump top. Inside the bellows is a O-Ring that needs replacement. It should be silicone greased during assembly. This Ring is reinstalled in the race inside the bellows lip and not around the flange of the top cover. Reassemble with a new lid O-Ring and you’re good to go for another 5 years. O-Rings $15.00. Total repair $50. bucks in materials and a tube of Super Lube, time 1.5 hours. Note these waste hoses are all under the water line and need to be double clamped with #316 stainless hose clamps, replace existing as required.

5. The vacuum pump also has duckbills and these are subject to failure due to wear, tear and age. Keep a set or two of Duck bills in your parts stores and replace as require or every few years. There is a recommended duty cycle to these valves, but I just change them periodically to avoid Murphy’s Law ruining a week end.

6. The toilet valve has a rubber seal around it. This seal should be lubed periodically. Don rubber gloves and while holding the valve in the open position reach inside the vacuum chamber and apply Super Lube lightly on the black seal. Don’t goop it on as that will just hold crud cause the loss of vacuum. The idea is to keep the seal supple and happy but not slather it up.

:grin:A happy skipper is one that treats his head system with passionate respect, diligent preventative maintenance, and above all crew discipline.

 

[Four Suns]

Sounds like Chad could be president of the "club"

 

[osd9]

..........

2. The Tank vent should have a anti siphon loop with the loop up and not down. If it is down, the loop will fill with condensation and affluent and plug the line. How do I know this, well the SR assembly technique of “upside down inside out” production often confuses the line workers who are clueless as to what they a building and how it is supposed to work. :smt021 In chasing down my odor problem I traced the vent hoses to behind the cockpit liner, behind the fuel distribution valve manifold to find what … Yes ... inverted vent line loops wire tied in the down loop position and plugged from years of residual build up of salt, crap, dust and stuff. Packed solid, couldn’t get air through it. :smt089 Solution was to cut out the loop, replace with a new line section with proper loops and the smell and negative pressure issues vanished. .........

I don't have any pictures, unfortunately, but when I bought my 1998 330DA, the holding tank was deformed....partially imploded so to speak. The two big metal strips that held the tank in place didn't even touch the tank around the sides or top and only held the tank down by the contact they made on the tank's corners.

I honestly didn't pay much attention to it, and unfortunately, neither did the surveryor, at purchase time. Anyway, in the first season of ownership, summer of 2001, I quickly found out that the vent tube and filter was blocked with 'crud'...... I don't know how long it was blocked up for, but I presume it got blocked for the reason Chad describes above, as the vent loop was down...actually more sideways.....

IMHO,the partially imploded, permanently disfigured holding tank, after reading this and many other threads on the net, was a 'product' of pumping out the tank with a clogged venting/filter tube.....I certainly won't be 'blocking' my holding tank vent on purpose anytime soon.....

 

[Four Suns]

Surprised the surveyor didn't say anything....

 

[carterchapman]

Thanks Chad!

Words to live by for my boat - as a new guy to vacuflush heads, I appreciate the time it took you to put that together.

Moderator - Chad's post needs to be a "sticky"!

 

[electricaldoctor]

Although the toilet bowl seal can leak and it's good to lubricate it occasionally with a little petroleum jelly, if the toilet is holding water, that's probably not it.

I note your boat is 12 years old. Have you ever changed the duckbill valves in it? When they begin to fail, they will allow the vacuum to escape out and the pump will cycle. When they totally fail, you won't get any vacuum... and you'll discover this after 3 people have gone #2.

The bellows pump you refer to does not need to be lubricated. If I were you, I would get a rebuild for the whole assembly and put in a new bellows and 4 new duckbills, put some lithium spray grease on the mechanical joints on the motor connected to the bellows and call it a day.

If you do want to lubricate the internals (because you *really* just want to), you can get some head lubricant stuff from West Marine (or your favorite marine store) that is made by Domitec and you can flush it down the toilet. I've never done that... but I always have someone putting things like toothpicks, pennies, dental floss, and juice box straw wrappers down my system so I periodically disassemble it anyway. (We have a ghost on the boat because NO ONE ever admits this stuff). Come to think of it... Dental floss in the duckbills has the symptom you describe...

What do you think guys ... do you think that I can get a few more seasons out of these bad boys?
~Ken

 

[captsearay]

Have you checked the switch on the vacuum tank? There is a rubber bellows that contacts a micro switch that gets cracked and leaks vacuum. You can't buy just the rubber part but you can have it rebuilt for much less than a new switch.

 

[WaterDoc]

Replacing duck bills didn't solve the 'cycling issue.' I really hesitate to replace the bowl valve and seal because that means taking apart the head completely to replace. I bought the assembly with the duck bills though. Vaseline didn't seal it. I may try a little vegetable oil...and if that doesn't do it....I'm left with taking up the toilet and replacing.