Macerator Discharge, Vented Loop?

[kthoennes]

Silly me, nothing is ever quick and easy. So I'm replacing the macerator pump. As long as I'm down there, I figure I might as well replace at least the easily-accessed sanitation hoses too, since the old hose is getting stiff and started to tear easily when I tried to pry it off the old pump. Photo of the area below. I know there's a seacock at the thru-hull which we normally always keep closed, but shouldn't there still be a vented loop in that discharge hose between the pump and the thru-hull? The top edge of the photo is the salon floor. The waterline is roughly even with the top of that big gray stringer you can see on the left side. Shouldn't I at least run the new hose up as close to the underside of the salon floor as I can, and install an anti-siphon valve at the top? (I searched the forum for this same question but didn't find an answer directly on point.) I know we don't heel over like a sailboat, but that hose and pump height always made me a little uneasy. Thanks.

(Yes, I need to tidy up the sump pump wiring and properly mount the float switch, that's a work in progress too.)

(You can also see where the vent filter cartridge used to be. Peggy was right of course, removing the cartridge and opening up some unrestricted airflow fixed a persistent odor problem.)
View attachment 120029

 

[koliver]

YES
You absolutely need that vented loop.
Mine clogged. The result was backflow through the macerator into the black tank. All was still OK until the tank vent hose came apart at the tank end. I heard water running, checked, and found the dribble from the tank into the bilge. Further examination of the system disclosed the clogged vented loop. There is a very tiny duckbill valve in the top of the loop, designed to allow air to enter the loop and liquid to be prevented from entering. When it fails, the above happens. Without that vented loop, the through hull connection feeds directly into the tank, filling it in reverse, through the macerator. Maybe a brand new macerator will protect you. Mine isn't, so didn't.

 

[boomerang]

Keith , he said he keeps his seacock closed. I don't see why he would need a vented loop. There's nothing for it to siphon back from.
Our macerator doesn't have a loop. Heck, the whole thing is below the water line but the only time the seacock is open is when the maserator is on. Behind all of that is the Y-valve that closes it on that end.

 

[kthoennes]

Thanks Boom. Yeah, that's why I'm asking. I assume it came from Mainship configured as it is now. We rarely open that seacock and discharge overboard anyway, but as long as I'm replacing the hoses, I figure I might as well do it properly. I'm just not sure in this situation.

 

[koliver]

Keith , he said he keeps his seacock closed. I don't see why he would need a vented loop. There's nothing for it to siphon back from.
Our macerator doesn't have a loop. Heck, the whole thing is below the water line but the only time the seacock is open is when the maserator is on. Behind all of that is the Y-valve that closes it on that end.

Quite right, until he doesn't close the seacock.
My seacock was installed before the generator, the muffler for the generator, the exhaust outlet through hull for the genset, the Espar heat pipes, and other stuff. It is in the fwd, stb corner of the ER, ahead of the fuel tank, in the 12" wide alley between the tank and the fwd bulkhead, so I can't reach it without removing a bunch of that after installed stuff. I put a valve at the tank to close the whole setup, but that was after having the previously described failure. I never assume others will have such easy access to their seacock that it can be readily closed.

 

[boomerang]

Thanks Boom. Yeah, that's why I'm asking. I assume it came from Mainship configured as it is now. We rarely open that seacock and discharge overboard anyway, but as long as I'm replacing the hoses, I figure I might as well do it properly. I'm just not sure in this situation.

There's more than one correct way, I'm sure. For our application, we don't need a siphon break. When it comes to plumbing, I like to keep the fittings to a minimum!

 

[kthoennes]

I think the link to my initial photo may have broken for some reason, I'll try again.

 

[porman]

Our Mainship has two holding tanks, two overboard diaphragm pumps, and two seacocks. No vented loops. The seacocks stay closed until we need to empty the tanks. Only when in Canada, of course, and also following their rules. I open a seacock, turn on the pump from the breaker panel, and watch the amp gauge. The gauge needle starts off with big, slow swings and after the tank is empty the needle goes to rapid, small swings. I turn off the breaker and immediately close the seacock. When in the US the handles for the seacocks are removed.

 

[rwidman]

The boat's manufacturer would most likely installed a vented loop if one was necessary. Unless you or a PO have modified the plumbing, I wouldn't think you would need to add one.

 

[gsholz]

There should be a vented loop to prevent back siphoning. But even then it is worthwhile to keep an eye on them (the vented loops).

A few years back I was wondering why my holding tank was always full. Turns out it was sea water siphoning back in. Cleaning the vent solved the issue. Religiously keeping the sea cock closed works too but is a pain offshore.