Macerator & Other Discharge Valves?

[quadrille38]

Thanks for everyone’s replies. Throughout this “quarantine” we have been on our boat quite a lot and had plenty of time to learn more about different things, including how a pump out using the thru hull works with our system.

I believe we do have a system identical to @quadrille38 as we have the same model boat and everything he’s described sounds the same.

Our head pulls fresh water and once flushed, it goes through the grinding macerator pump and directly to the holding tank. There is no other route possible between these two points. Next, we have the option to pump out at the dock, or using the thru hull out at sea. To pump out using the thru hull, the valve downhill just before the macerator pump must be opened, along with the thru hull itself.

We recently took our boat out offshore to attempt a pump out to make sure all works well. Unfortunately it didn’t work out as well as we would have hoped.....

We opened the valve and then the thru hull, pumped her out, closed the valve first, then the thru hull. It was at that point we noticed a small leak start to spread from under the macerator pump. We dried and cleaned the area, placing paper towels to catch any further drip. We checked it the next day and see that it still has a tiny leak. This area is quite tight to get into. Worse than when we had to change the macerator pump (both are Jabsco pumps) next to our head which also ended up getting a small crack in the plastic and ended up leaking too. I’m not sure if that’s what has happened here, or if we shut the valves in the wrong order, leaving discharge in the lines that may have caused pressure to leak out somehow, and/or both. Is there a specific order in which the valve and thru hull should be opened/closed? Any thoughts?

I never actually pump out through the macerator because it’s illegal here in the Great Lakes but that said I do have to winterize the system and that requires opening the valves to pump antifreeze from the holding tank through the macerator. In the spring I close up and lock up the discharge valve So here is the order I think makes sense.

To discharge open the valve in front of the macerator, then open the through hull and quickly turn on the macerator. When the tank is empty, shut off the macerator and quickly close the through hull. Then close the valve in front of the macerator.
Mr reasoning for this order is that when the through hull is open without the pressure created by the macerator, water can flow up the hose Towards the macerator and eventually towards the holding tank.

 

[pumpkinpie]

Thanks so much for your response @quadrille38. That’s exactly what we were thinking also. My mistake this time since I wasn’t using my head and shut the valve first instead of the thru hull. Maybe that’s why it was leaking with the water in there between the macerator pump and thru hull when there typically hasn’t been. Possibly from back flow pressure up to the macerator.
Do you think we could get rid of the excess water/discharge in the line by keeping the valve shut, quickly open the thru hull, and briefly letting the pump run to pump out any water left in the line, and quickly shutting the thru hull again?

 

[Scott T-Bird]

Do you think we could get rid of the excess water/discharge in the line by keeping the valve shut, quickly open the thru hull, and briefly letting the pump run to pump out any water left in the line, and quickly shutting the thru hull again?

First, it is a very bad idea to close either valve before operating the pump. You have to accept that some seawater is going to back up in the line before you get the thru-hull closed. If you have a small leak, it is a problem that should be fixed with your hose clamps or your pump.

Second, I'm confused with the description of your system. Do you have 2 macerator pumps? That is how I read your description. It sounds like you said you have a macerator pump between the toilet and the holding tank. Then it sounded like you have a macerator pump between the holding tank and the thru-hull for pumping out at sea. (I understand that your deck pump-out pulls from the holding tank when you have the y-valve turned the right way). Perhaps that second pump isn't actually a macerator and simply a waste-water pump? I might be mistaken, but I thought the macerator pump is usually a pump that pumps out the holding tank to sea-water in the manner that you have described, so it may be more likely that your pump ahead of the holding tank isn't really a macerator pump and is really just a flush pump for the toilet? That's why I'm confused about your description.

A macerator pump is essentially a grinder pump for grinding solids. I'm not sure a macerator pump is really necessary. Many boats don't use a macerator pump at all. Having 2 macerator pumps would be gross over-kill. If you are grinding solids on the way in to the holding tank, why would you need to grind solids on the way out, and vice-versa? . Besides that, macerator pumps can be (unnecessary) trouble with all the extra mechanical gear. I think they are prone to failure. I've heard that sailors simply remove the macerator pump and replace it with something more reliable.

Also, why do you need a pump between the toilet and the holding tank? Doesn't the toilet have a hand flush pump, or an electric pump for discharge? I can't imagine why you need a pump between the toilet and the holding tank, unless you are talking about a toilet that doesn't have a pump?

You might be better off changing your plumbing to discharge directly from toilet to sea and by-passing the holding tank, with a y-valve for directional discharge either to holding tank or sea thru-hull, of course. This way, you can avoid the redundant pumps altogether. Many boats operate like this without the need for any pumps, except the toilet flush pump.

 

[quadrille38]

It’s generally a bad idea to run a pump dead headed.
If it’s really a concern, have someone operate the macerator while you stand ready at the valve. The second the pump is off quickly close the through hull.

scott

If it’s the same set up as mine and from what we’ve discussed I think it is. The toilet has a grinder pump so that when you evacuate the bowl it grinds the waste as it shoots it up into the holding tank.
The deck pump out pumps from the holding tank.
There is no Y valve.
The line for the macerator comes off the bottom of the holding tank, there is a valve in this line right in front of the macerator. The discharge from the macerator goes to the through hull.

 

[Terry Cox]

Different model boat here, but ours is very simple. Both electric macerator toilet pumps discharge to the holding tank. Holding tank has a wye fitting (no valve) with one hose that connects to the deck pump out fitting, the other to the overboard macerator pump and through hull valve. Panel has a toggle switch to turn on the the macerator pump. Where legal, I will open the through hull valve, then turn on the macerator pump until the tank is empty. If I've used the overboard system while cruising, upon returning, I will flush the holding tank until water is clear, as well as the holding tank vent, from the pump out hose. With a little fresh water left in the tank, I will discharge some fresh water through the running macerator and through hull valve to rinse away any sea water residue.

Vanity sinks drain overboard above the water line and the through valves are most always open unless heeling is expected. Galley sink drains below the waterline. Through hull valve is always open while cruising, but closed when we're away from the boat.