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!

seacat96 said:

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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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?

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.

menzies said:

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?

Click to expand...

I once had the same problem and the solution you recommend worked for me.

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.

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

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

Don't shoot the messenger here, but....

Is your through-hull open?

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.

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.

seacat96 said:

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. View attachment 112850

View attachment 112851

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Where does the other line off the Y go?

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

Ted

Your pump has 2 duck bill valves on either side of the pump. They don't last forever.

Ted

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.

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.

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.

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.

The only thing worse than working on a head is not having one. Double the fun

Peter

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.

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.

O C Diver said:

Your pump has 2 duck bill valves on either side of the pump. They don't last forever.Ted

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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.

--Peggie

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.

Sewage pump won't pump

We recently had a similar problem: discharge pump would not empty holding tank, but pump out boat or shore station would. After replacing the pump with almost no detectable improvement, I tightened all of the hose clamps (again). One pair had rusted a bit, and sure enough, they were not tight. Replaced the hose clamps and tightened down and now new pump works perfectly.

seacat96 said:

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!

Click to expand...

Was the issue resolved? Cause?

Sailor Harry said:

We recently had a similar problem: discharge pump would not empty holding tank, but pump out boat or shore station would. After replacing the pump with almost no detectable improvement, I tightened all of the hose clamps (again). One pair had rusted a bit, and sure enough, they were not tight. Replaced the hose clamps and tightened down and now new pump works perfectly.

Click to expand...

Did you keep the old pump?

I had the same problem once as Juliet15 in my Lien Hwa 47. We did not have Vacu-flush but in trying to figure out what worked and what didn't on a new to me boat, I turned on the macerator switch without having opened the valve. Inverted duck bills only be came evident when, out to see for a long weekend with guests required pump out. There is a 3' tall riser in that pump out system to prevent water coming in from the outside which of course collected sewage. When I disconnected the hoses, it all rushed out at me. Fortunately, on that boat, that area of the bilge was isolated and with a bilge pump. I was able to clean up by bringing salt water from the anchor washdown hose. But, I didn't have extra duck bills so we had to go to shore, pump out at a dock, and then, when I got home, go through the whole messy process again when I got the valves. God I love boating.

My father was a plumber always said, It all washes off.

Pay attention to left hand threads

I have seen several of boats with this pump that had turned on the pump before opening the sea cock. This caused a very high pressure on the outlet side of the pump and caused the duck bill valve to invert. The solution is to turn the valve back right side out. These pumps have left hand threads on the nipple that has to be removed to get access to the rubber valve. I have seen several pumps ruined by turning the nipple the wrong direction. If you don't have replacement valves then turning the valve back right side out will usually get the pump working again but while you have it out it is a good time to put in a new valve. Buy the way this is a translucent bump housing and you can shine a flashlight through the pump and see when the pump empties the tank.

Shay

This problem was solved - and it turns out it was the check valve in the system (that didn't need to be there) downstream of the pump but before the thru-hull overboard valve. Sorry for the late reply.