Blackwater tank discharge question

[HodagSailor]

Hello all,

I'm a long time follower of the forums, but this is my first post.

My new sailing catamaran came plumbed with only one discharge hose coming from the top of my blackwater tank, and it runs directly to a macerator pump. Downstream of the macerator pump is a Y valve with one hose leading to a through hull just above the water line, and the other to the deck fitting for pump out. I have the valve on the hose to the through hull closed (Florida coastal waters). When I pump out the tank at a marina, I'm sucking the material through the macerator pump, which is not running. Seems to me the chunks could get caught in the impeller, and since the pump only allows fluids to pass in one direction, I cannot add water from above to "rinse" out the tank.

Is this set up correct? Anyone else have a set up like this?

Thanks for any thoughts and opinions.

I'll try to attach a photo of the set up:

[rslifkin]

I would move the tee to between the macerator and tank. Then you either pump through the macerator and out the through hull or (with the overboard discharge valve closed) suck it out the deck fitting (without going through the macerator). That's how mine has been plumbed since the boat was built 38 years ago and it works well.

[peghall]

There should be a y-valve instead of a tee in the line between the tank and the macerator pump. Keep it aimed at the pumpout fitting except when you're dumping the tank (legally of course). To rinse out the macerator pump, first pumpout and rinse out the tank...it's not necessary to fill the tank with water to do that. After you've pumped out, put 4-6" of water into the tank VIA THE DECK PUMPOUT FITTING...that sends the water into the tank at the bottom to stir up any sludge and hold it in suspension. Pump that out. Repeat, repeat until you're pumping out clean water. Then add water to the tank one more time--again via the pumpout fitting and let the water keep running this time while you turn on the macerator to rinse it out.

If you do this at least every 2-3 months, better yet, after dumping the tank each time using a washdown hose, you'll have fewer problems with your macerator pump 'Cuz waste is sticky...rinsing it out of the macerator keeps the impellers spinning freely.



--Peggie

[rslifkin]

A Y valve to select between the macerator and deck fitting is ideal, but as long as the macerator seacock is closed after use (so water can't be pulled backwards through the macerator) a simple tee works just fine. The only caveat is that the seal on the pumpout cap has to be good otherwise the macerator will pull air past the seal and have a hard time emptying the tank.

[HodagSailor]

Here's my corrected black water tank plumbing.
Thank you all for your suggestions.
Next project is to correct the wiring.