Fitting holding tank macerator

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I am on the point of fitting a holding tank macerator. My tank and sea cock fittings are 38mm. The macerator input is 38mm and the output is 25mm. The chandler tells me that I can use a Vetus adaptor (cut as required) to match, which sounds OK. The present arrangement is a plastic Tek Tank (one year old) pumped from the top by a Henderson hand pump, up well above the waterline in a loop, and back down to the sea cock. The top of the holding tank is more or less on the waterline. It would be convenient to fit the macerator just above the tank and take the macerated output straight down to the sea cock without looping up over the waterline. Is there a disadvantage in doing that? Are there any tips or suggestions anyone can make...? Peggy /forums/images/graemlins/smile.gif
 
Put the macerator at least 6-8" above the waterline, then to the thru-hull. That will provide what amounts to an acceptable loop im the line. However, you'll still have to keep the thru-hull closed when not actually using to empty the tank.

If you plan to use the same thru-hull to discharge the toilet overboard AND dump the tank, you'll need a y-valve in the tank discharge line, not just a tee or wye.
 
Thank you, Peggy. I am very tight on that 6". If the sea cock it to be closed when not actually discharging - i.e. never left open unless closely attended - then do we need a loop at all?
 
Yes...for two reasons: 1. The tank--or part of it, including the discharge--is below waterline. Without a loop, sea water trying to enter the tank when the trough is open would create backpressure--quite a bit of it when dumping the tank while the boat is underway. 2. People are fallible...if the seacock should be left open, water would flood the tank. The macerator would only slow it down, it wouldn't prevent it.

All loops should be at least 6-8" above waterline AT ANY ANGLE OF HEEL...which can be 3-5 FEET above resting waterline on a some sailboats. If you don't have that much room, at least put the macerator above the top of the tank.

And put a y-valve in the discharge line, close to the tank discharge fitting, so you can cut off the flow to the macerator to replace the impeller or service it. 'Cuz nobody every discovers that the macerator isn't working when the tank is empty, only when it's full.
 
We went down the macerator route a couple years ago. After unclogging the macerator many times because of the things being discarded down the toilet that shouldn't have been discarded I eventually did away with it and went for the electric henderson type of discharge pump. My advice is to go straight for this route. If you can replace your manual henderson with the electric version then it's an easy swap. In our case the manual holding tank pump out became a second manual bildge pump.
 
Thanks and thanks to you, Peggy. One of the reasons for going down the macerator route was to get easy to manage 1" pipe so we can re-route it outside the wardrobe area, where the present pipe runs; while it is not terribly smelly, there is enough smell to make it unacceptable in a wardrobe. I was already getting worried but the idea of a macerator and you have confirmed my fears. Thanks, it would have been a mistake for us, I think, as not all of our guests seem to appreciate that they will have to make the slightest adjustment to their behaviour when on a boat. Incredible, but true! I like the sound of the electric Henderson - I'll look into that in the local chandlery.

Peggy, your comments about 6" minimum applies for the electric Henderson as well as a macerator, no doubt?
 
I agree with Talulah...an electric diaphragm pump is by FAR the better way to go. And yes, it should also be above the top of the tank.

Talulah, apparently you need to educate your guests a bit more about what marine sanitation systems can and cannot swallow and "digest." Or make new friends who are educable. /forums/images/graemlins/smile.gif
 
Maybe.....

One of these might be in order
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