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Old 01-15-2021, 02:22 PM   #1
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Sewage Dischare Issue

On a recent run outside, I tried to pump out the holding tank. Open the seacock and turned the diaphragm pump on - it made all the right noises except after about 10 minutes of pumping it was clear nothing was happening. There's a check valve immediately after the pump and of course the suction going into the bottom of the tank. Any ideas on how to troubleshoot? Thanks in advance for any advice!
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Old 01-15-2021, 02:25 PM   #2
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On a recent run outside, I tried to pump out the holding tank. Open the seacock and turned the diaphragm pump on - it made all the right noises except after about 10 minutes of pumping it was clear nothing was happening. There's a check valve immediately after the pump and of course the suction going into the bottom of the tank. Any ideas on how to troubleshoot? Thanks in advance for any advice!
Open the deck fitting (carefully) to ensure the vent isn't clogged and not allowing air in to replace the black water.

Is your pump self-priming?
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Old 01-15-2021, 02:59 PM   #3
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Something to Try I guess though it does vent when I pump out at the dock and that often is a reasonably tight fit. The pump is located at about the same level as the bottom of the tank so priming should not be a problem.
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Old 01-15-2021, 03:05 PM   #4
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Open the deck fitting (carefully) to ensure the vent isn't clogged and not allowing air in to replace the black water.

Is your pump self-priming?
I once had the same problem and the solution you recommend worked for me.
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Old 01-15-2021, 03:24 PM   #5
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Why is there a check valve after the pump? Seams like a likely place for a clog to form.
The vent was my first thought also.
Lots of other places for problems.
Blockage between the pump and tank.
Bad valves in the pump.

My suggestion is to check the vent first. If that isn’t the problem, I’d look for a clog at the check valve. Next I’d look at the pump and suction line.

Be sure to let us know when you find the problem.
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Old 01-15-2021, 06:18 PM   #6
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As a curiosity, your tank has 2 suction ports (1for overboard and 1 for dock side)? Many have a y valve where you have to select the which way you are emptying the tank. Did you flip the valve? Also, if it's a diaphragm pump, when was the last time the valves were changed? Might help the diagnosis to post some pictures and identify the pump manufacturer.

Ted
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Old 01-15-2021, 06:25 PM   #7
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What type of system is it? Example , a sealand discharge pump has duck bills on both sides of the pump. A macerator pump could have cutter blades and a pump impeller. We need more info. If you have on suction line I the tank and a Y valve then as said valve is in the wrong direction or pump valves
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Old 01-15-2021, 06:49 PM   #8
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Don't shoot the messenger here, but....

Is your through-hull open?
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Old 01-15-2021, 10:12 PM   #9
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Although not currently at the boat - the manual says the discharge pump is a Sealand T-Series Model 301200 Holding Tank Discharge Pump. I've also attached a pic of the pump and you can see the check valve on the discharge size. One thing I did not remember - until I looked thru my pics - although the pump is located at or below the base of the tank - the suction side goes thru the top of the tank with a tank riser connected that goes to / near the bottom of the tank. Click image for larger version

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Old 01-15-2021, 10:34 PM   #10
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Could be crud solidified in the suction tube, especially if you don't use it often. At least with a dip tube you should be able to pull it out without emptying the tank. Can't do that with a bottom drain.
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Old 01-15-2021, 11:01 PM   #11
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Quote:
Originally Posted by seacat96 View Post
Although not currently at the boat - the manual says the discharge pump is a Sealand T-Series Model 301200 Holding Tank Discharge Pump. I've also attached a pic of the pump and you can see the check valve on the discharge size. One thing I did not remember - until I looked thru my pics - although the pump is located at or below the base of the tank - the suction side goes thru the top of the tank with a tank riser connected that goes to / near the bottom of the tank. Attachment 112850

Attachment 112851
Where does the other line off the Y go?

Is the dock side pump out line part of that system?

Ted
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Old 01-15-2021, 11:04 PM   #12
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Your pump has 2 duck bill valves on either side of the pump. They don't last forever.

Ted
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Old 01-15-2021, 11:04 PM   #13
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Time to put on some gloves. Take that pump out. Get a hose in the suction line. Blow it back. Take off the hose barbs from the pump. Replace the duck valves . Their cheap . Good for the next 10 years.
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Old 01-16-2021, 12:47 AM   #14
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In my (bitter) experience, with most macerator pumps anyway, they end up not being truly self-priming, even when mounted quite low. They say self-priming to 1 metre - b/s in my experience.
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Old 01-16-2021, 06:36 AM   #15
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A diaphragm pump is very poor at lifting , any tiny air leak and it stops working.

Of course if the pump is located below the tank, it will probably work well for a long time.

Our setup would have taken a huge effort to relocate the pump , so we simply used the deck fitting to overfill the tank. This filled the waste pump and it operates fine.

In a marina setting frequently rinsing the pump with fresh water by refilling the waste tank and allowing it to pump the tank will get rid of the usual, paper stuck to any check valves .
Having the marina pump the tank usually bypasses the waste pump, so is no help.
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Old 01-16-2021, 06:57 AM   #16
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Rule out vent by opening the deck pump out opening. Get rid of the check valve, replace the duck bill valves. After that it gets messy - sclorotic hoses or clogged thru hull.

I had a macerator crap out right before a long trip. Worse, new replacement made all the right noises too but was functionally DOA so I chased a bunch of other issues thinking it was an install error. A day and a half and a half gallon of clorox later I finally got a second new macerator and it worked fine.

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Old 01-16-2021, 08:16 AM   #17
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Your pump is generally known to be a very reliable pump. It is always highly recommended by Peggy Hall, the Head Mistress. It is not a macerating pump. As several others have suggested, eliminate the other possibilities before going at the pump itself, especially that check valve for which I see no point. If after opening your deck port to check your vent doesn't solve the problem, if it were I, I would next remove the check valve. It serves no useful purpose and just adds another failure point. By the way, if you have a filter in your vent line, remove it.
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Old 01-17-2021, 09:46 AM   #18
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Its gross!!!!!

But a sealed diaper pail for the toilet paper should stop most of the flap valves and duck bills from collecting paper and leaking.
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Old 01-17-2021, 11:41 AM   #19
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Your pump has 2 duck bill valves on either side of the pump. They don't last forever.Ted

You're confusing the S-Pump (vacuum pump in a VacuFlush system) with the T-Pump (overboard discharge pump). The S-Pump has 4 duckbills--2 on each end of it...the T-Pump has only two--one on each end.

In fact, that's the ONLY difference between them except about 100% difference in their price. And in an effort to prevent VF owners from saving money by replacing an S pump with a T pump, SeaLand (now Dometic) reverse-threaded the valve nipple on the T-pump to make it impossible to just add another valve nipple at each end. However, that hasn't stopped a lot of VF owners from replacing vacuum pumps with T-Pumps anyway...the lack of duckbill redundancy may require slightly more frequent replacement, but it otherwise works just fine.

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Old 01-22-2021, 03:43 PM   #20
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One last suggestion, learned from experience:

If you turn the pump on before opening the seacock, or before opening the Y valve the strong pump suction will turn the duck-bill valves inside out.

I have that same pump. Don't ask how I know this.
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