Pump Out Macerator Pump filling holding tank

[Mainship Pilot]

Hi there, 2004 Mainship Pilot 30, seems I'm gaining water vs relieving water! I empty my tank underway, and look a bit later, and tank is full again. I'll assume there is some kinda check valve in the macerator pump? I'm guessing its an origional pump, shoulda taken a picture, but forgot. Is the fix to replace the pump, or is there soemthing easier? Kinda tight in there! Guess I'll have to do it the old fashion way, shut off the seacock to the macerator and pump out at the pump out station thru the deck fitting in the mean time. BTW,. it's a salt water head.

 

[SteveK]

OK, I am curious to know why.
Is this a new event, as in was it working correctly and now does not. Is the thru hull below water line and is the macerator also below water line.

 

[Mainship Pilot]

Yes and Yes, This is a new event, my tank was not filling up on it's own before, and the thru hull is below the waterline, the Macerator pump may be about even with the waterline, give or take an inch, mounted just above the seacock behind the holding tank. I figure I can close the thru hull when I get to the boat tommorrow AM, and go to a pump out dock and pump the tank dry, however, will need to fix eventually, unless there is a quick fix, someone is aware of? I'm guessing a 20 year old pump has lived it's life well in a salt water environment.

 

[Brisyboy]

Before blaming the pump - check the anti-syphon valve you have in the pump out hose - if blocked it could be sucking the discharge right back in - with a lot of sea water of course

 

[Mainship Pilot]

Hummm, I don’t recall seeing an anti siphon valve in the train from the end of the holding tank to the sea cock anywhere. I’ll try to post a picture tomorrow when I get there, and let you guys tell me what you see. Thanks!

 

[HeadMistress]

There should be a vented loop in the tank discharge line between the macerator pump and the thru-hull...bu in the absence of one there's another simple solution:: keep that thru-hull closed except when dumping the tank and be moving very slowly when you empty the tank. Macerator pumps can slow down water being forced up them through an open thru-hull, but they can't block it completely..

--Peggie

 

[Mainship Pilot]

Thanks Peggy, That’s obviously a solution, but I guess I still have to ask, the tank never filled itself before, now suddenly it’s doing it. Am I correct in my assumption that the pump is just on its last legs, or is there something else there? Thank you!

 

[SteveK]

AS suggested close the thru hull valve, go to you dump site and empty tank, then immediately close valve. Confirm tank is empty.
Remove the pump from hose between thru hull and pump. If there is no backflow preventer then the vanes in pump are allowing water in.
Oh, and as Peggy said there should be a vented loop since this is below waterline. I am guessing you do not have a vented loop.

 

[Mainship Pilot]

Ok, So the backflow preventer is connected between the end of the Mac pump and the hose to the seacock, I’ll look for it. Please understand that these Pilot 30s have big boy systems in little boy spaces, so seeing things and especially working on things is a real challenge! As for the vent, the holding tank has a vent, but I’m guessing you are referring to something different. I’ll update tomorrow either after I pump out of after I get to the Island. Thank you!

 

[SteveK]

Not exactly. You either have a backflow valve or a looped line. You need to determine which one was keeping water filling the tank.
My guess is you do not have a looped line and may have a backflow that is not sealing. So look for a loop line before taking things apart.

 

[Mainship Pilot]

Ok, So the hose from the top of the seacock goes straight up to about the Mac Pump, does a U down, then a U back up to connect to the pump, call it a 5/8 ish inch hose, it doesn’t loop in a circle, but forms an upside down U if that makes sense?

 

[SteveK]

Ok, So the hose from the top of the seacock goes straight up to about the Mac Pump, does a U down, then a U back up to connect to the pump, call it a 5/8 ish inch hose, it doesn’t loop in a circle, but forms an upside down U if that makes sense?

Perfect sense. should have said it like that to you. The top of the loop is well above water line, correct? Then the little breather at the top of the 'U' is called an anti siphon that lets air in to stop backflow. It is most likely plugged. That is where you start. Clean if possible, replace otherwise.
Even after fixing, close the seacock when not in use.

 

[Mainship Pilot]

Will do, will check it out tomorrow when I get there, don’t remember seeing a breather, just the hose, but that doesn’t mean it’s not there. Thank you so much!

 

[Mainship Pilot]

Here’s pix. shut off seacock and emptied head.

 

[SteveK]

Where does the blue stripe hose connect, under to the macerator?
Where does the white hose connect, to the bottom or top of the holding tank?

From what is pictured you do not have a backflow or a vented loop above waterline from the thru hull.

 

[Mainship Pilot]

Yes, Bottom of Pump and bottom of tank. I’ll be shutting the seacock off from nowon!

 

[ranger58sb]

Hi there, 2004 Mainship Pilot 30, seems I'm gaining water vs relieving water! I empty my tank underway, and look a bit later, and tank is full again. I'll assume there is some kinda check valve in the macerator pump? I'm guessing its an origional pump, shoulda taken a picture, but forgot. Is the fix to replace the pump, or is there soemthing easier? Kinda tight in there! Guess I'll have to do it the old fashion way, shut off the seacock to the macerator and pump out at the pump out station thru the deck fitting in the mean time. BTW,. it's a salt water head.

Didn't read all the responses, but did you close the seacock right away after dumping? If not, the holding tank will sometimes (often? usually?) back-fill...

-Chris