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Old 12-09-2004, 05:48 PM   #15
Rivet Master
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1978 31' Sovereign
Texas Airstream Harbor , Zavalla, in the Deep East Texas Piney Woods on Lake Sam Rayburn
Join Date: Jan 2003
Posts: 2,435
Images: 292
Originally Posted by malconium
......I had originally been thinking of an arrangement similar to what is in the attached sketch - except without the T between the macerator and the dump valve. Does this seem like a better overall approach?
Personally, I think it is, because the "extra" Tee connection could either be used as a conventional dump, or, as I have done, install a water hose inlet with a valve to both wash the tank and provide "extra" water for the macerator pump....BTW, I have never had a problem with the pump grinding up anything I have thrown at it....had never had a water hose hooked up to the valve. I had read "Phred's" site previously - I do not see the requirement for the isolation valves he had before and after the macerator pump - the main tank valves should suffice to permit pump repair/maintenance....

I have never pulled the pump for maintenance - nor do I intend to - it might last 10 years or more - I prefer to take my chances with it lasting....bear in mind, the climate here in Houston is such that I do not winterize - if a really cold spell were to be on the horizon I would throw a bit of antifreeze at it, and I keep a small electric heater in the cabin set to the lowest setting.

Originally Posted by malconium
......I notice that your assembly uses a 1-1/2" connection to the macerator. Do you think there is any advantage one way or the other for 1-1/2" vs 3"?
The Jabsco I purchased had a 1 1/2" inlet - it was a heck of a lot easier to run the 1-1/2" instead of the 3" - plus, with the head of water from the gray water tank, I feel as is if I have a pretty good chance of pushing a "plastic slug" through the 1 1/2" line without too much difficulty. The downside of a 3" suction is possibly loosing the pump suction with a couple of inches of water left in the tank -- read below.

Originally Posted by malconium
......The standard macerator pump I am looking at comes with the 3" connection and the pump body itself is pretty much the same diameter. Perhaps this approach would still not put the pickup point for the "plastics" low enough. What do you think?
More than eliminating the solids, I would worry that it would loose suction and not pump all of the water out of the tank - giving credence to John's (74Argosy24MH) comments above - gravity works. For my particular setup, the installation of the macerator pump was absolutely the best thing to do - easy to set up, store, and cleanup the 1 1/2 inch discharge hose and with half unions at each termination everything gets buttoned up in seconds after pumping the "load". I used 1 1/2 inch hose (the pump outlet is 1") because I found a very sturdy PVC flexible hose that would not collapse and was "slick" on the inside - with the 1 1/2" hose I eliminated a lot of discharge head, allowing the pump to evacuate the tanks faster, and allowing for additional sections of 1" or 1 1/2" hose should I find that I would have to pump a good distance to get to a disposal inlet (with 1 1/2" discharge hose I am certain that I could pump at least 100’ into a toilet or similar disposal point).

Originally Posted by malconium
Part of the reasoning for using a combined gray/black tank was that the extra water would help keep the solids in suspension and might help break them up better. Again what do you think?
Since you asked....I do not like the idea of a single combined tank at all.....too much chance of odors and other "stuff" backing up into the sink or shower drains (especially the shower)...
Typically the solids do not stay in a holding tank long enough for the aerobic/anaerobic process to do much good as far as suspending the solids....I think that after a weekend of camping the bottom of the black water tank looks pretty much as the bottom of the toilet after the typical male takes a dump - only that it contains a heck of a lot more volume of everything. By “rocking” my black and gray water tank (pumping the black tank, equalizing the gray with the black, pumping the black again, equalizing again, pumping the black one more time, equalizing one last time, and pumping the gray dry) I feel as if I am getting the black tank as clean as possible without having wash jets installed in it. By leaving a few gallons of the gray water in the black water tank I think I leave enough pure fluid to help dilute the “plastics” as soon as they hit the tank, hopefully eliminating the dreaded “brown mountain” that I have personally witnessed, fought and ultimately was victorious over – but at a personal cost.
Another reason for keeping the two water systems separated, IF, at the end of a long weekend, someone really needs to take a shower and the tank(s) are nearly full, with two tanks I can do one of two things – transfer a bit of the gray water to the black tank, or drain a couple of gallons of the gray tank on the ground (or blue tank) so you don’t have to break camp prematurely – I’m not advocating surface disposal of gray water, but in some instances it is still acceptable.
I REALLY do not like to mess with a blue boy with the contents of a black tank in it.
Like I said, the installation of a macerator pump certainly worked for me, but each individual has to analyze their own circumstances.


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Old 12-10-2004, 01:28 AM   #16
Rivet Master
1973 31' Sovereign
Portland , Oregon
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It occurs to me that maybe I should design a mount for the macerator pump that could pivot downward when it was time to run the pump. I could picture using flexible rubber tubing between the tank and the pump that would bend downward when I lower the pump. The pivot point of the framework could be near the tank. This way the pump could be stored relatively high and used in a position that was definitely below the bottom of the tank so that gravity would help.

Another alternative might be to use a detachable macerator pump. Take a look at the following item:

This pump looks like it would mount pointing downward so it would definitely be helped by gravity. I think I still like the idea of having the pump permanently attached.

By the way I am intending to use a 1 way valve between the grey/black tank and the shower to prevent reverse flow. The idea to do so came from these forums and it seems like a good one.

Right now I guess I need to hurry up and get the rest of my floor replaced so that I can begin to zero in on the rest of the stuff.


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