Tuesday, February 1, 2011


Macerator pumps provide a partial answer to sewage disposal, chopping waste into a thin slurry and pumping it out through a garden hose to a proper disposal. And that's all there is to it. They're not magic and they're not maintenance free. They can, though, eliminate the most onerous part of the dumping chore if used properly.

Most RVers use macerators in a temporary fashion and only when a full hookup is unavailable. In doing so, they miss out on some of the real benefits of a macerator. Temporary hookups involve adapting a macerator to an RV sewage outlet and attaching/reattaching it just as you would a "slinky" sewer hose. While this allows pumping sewage long distances and into otherwise unavailable receptacles, like septic tanks, plumbing cleanouts, sewers, or toilets, it also requires handling something even more clumsy (and prone to spilling) than a regular slinky. Storage and electrical connections (macerators demand hefty wiring) can also be a problem in this case. (See later for pointers on using a "temporarily" connected macerator.

Many of us have found that installing a macerator in a semi-permanent fashion is a far better way. Semi-permanent means that it can be used without attaching and disconnecting and it can be bypassed with valves and can be easily removed for maintenance. Carefully installed, a macerator can be used full-time with only a flick of the wrist and nary a drop of spillage.

Many of us feel the semi-permanent connection above is best, but temporary connections can work well and in some cases are preferable. You may not want to build the plumbing. You may not have sufficient room. You may trade RVs frequently. You may have two separate sewage system at different ends of the RV (some motor homes) and don't want to join them or plunge for two macerators. (Though two macerators are nice since you have a spare.) You may want to use the macerator on more than one RV. Don't, though, plan to be a good sport and dump for all your neighbors. It's a nice gesture, but you will be taken advantage of and you will soon tire of the odious chore, your macerator will wear out early, will overheat and may be damaged. Let them buy their own. Save the generosity for genuine emergencies when a neighbor really needs assistance.

Some Tips:
• Don't skimp on wiring just because it's temporary. Run stout wiring as described above to a connector near where the macerator will be used and use some form of plug-in connector from there to the macerator. If you try to run a flimsy, # 18 gauge, household extension cord to the battery and attach it with alligator clips, you will, eventually, get in trouble.
• Don't ever follow the old RV tip of simply cutting a hole in a sewer cap, bolting the macerator to it and connecting it directly to the RV sewer outlet. At best, sooner or later one or more sewer cap ears will break and you'll end up with poop all over yourself and everything else. At worst, you'll break the fitting attached to the RV with the same results and a much more difficult repair.
• Attach the macerator to the RV temporarily through a short piece of flexible hose. A piece of slinky will do but won't last long. You can get better stuff from plumbing, irrigation or auto stores like Big A that sell large diameter water hose for trucks by the inch. Use as short a piece of hose as possible, but enough so the macerator will be supported either against the RV, hanging from a bracket on the frame or lying on the ground. For temporary macerators the model with a 3" slip-on inlet is easy for attaching hose. The 1½" inlet can be adapted easily too (and is sold as a kit in RV magazine ads if you can't figure it out for yourself).
• Support, again, is important. Ideally, mount the macerator on a board or something that you can hang from a bracket on the RV and keep things out of the mud.
• Use a switch to control the macerator. (You don't have enough hands to disconnect wires and operate valves at the same time.) Mount the switch in a waterproof box attached to the support above. Don't just bore a hole in the board and stick the switch in it - it'll get wet and corrode.
• Keeping the inside of the macerator wet or lubricated (see MAINTENANCE below) is even more important with a temporary macerator since you might leave it packed away for months.

If it's an occasional shot, just stick the end of the hose in a sewage receptacle and let'r go. Use your imagination. Flush toilets are good (you don't need to hold the flush lever down; water flows through the built-in trap in a toilet.) Pit toilets are EZ, but the ranger might complain--be discreet. Gopher holes are good (don't worry about the gophers, they'll adapt -- and Darwin will account for those who can't). Sewers work--but make sure a storm drain (that can look like a sewer) doesn't drain into the pretty stream nearby. Shrubbery and trees are good--you'll be improving their growth--Anne's trees and roses grew phenomenally when I parked in her back yard.

DO NOT macerate into a garden that has edibles in it! DO NOT macerate--repeatedly--where the stuff will work its way toward someone's well. Macerating occasionally won't hurt anybody any more than the dog poop that can occur anywhere. Macerating repeatedly in the same place can work its way into the water system--be cautious.

If you're on a hookup in a park and need a positive fitting to the sewer receptacle, the RV store has three-inch and four-inch screw-in connectors with a garden-hose-thread fitting built in. The trouble is the fitting goes straight up. You don't want that. You want a nice, gentle curve so stuff will flow easily. You can do this with a hose "ell" from garden or RV stores.

If you're tapping the fitting cleanout plug on someone's house, buy a (cheap) threaded bushing to fit the fitting and screw a garden hose connector to it. Caution: The access cleanout plugs on houses work well, but many have never been used for years and have become plugged with debris. Check these out first by shooting some clean water through. No point in pissing off a friend or daughter-in-law by filling his/her kitchen sink with poop.

At rallies (fairgrounds) and similar institutions you can find plumbing cleanout fittings all over the place. Some buildings won't have an exterior vent pipe but will have a vent pipe on the roof You can run the macerator hose up to those unless the building is extraordinarily high.

If you have some privacy, you can also, literally, water the lawn with your macerator by spraying the stuff around a bit so it doesn't puddle up. The smell won't linger more than 5 minutes (if you've a good system--see elsewhere) and try to do it at night if people can see you (by morning there won't be a trace). Watering the lawn or similar dumping in the open must be done with caution. The macerated material (black and gray) is biodegradable and won't "pile up" as if you dumped the raw stuff from the tank, but if you dump in the same place frequently, food particles will accumulate and you can create a bad vector control (bug and rodent) problem.

Some of these methods are controversial. Some are illegal in some places. Use your head. One RV, in one place, with some space, can do all the above without damaging the ecology. A bunch of RVs dumping on the ground will create the equivalent of a cattle feed yard--unhealthy and dangerous.
For instructions on building a semi-permanent macerator system, as well as lots more great poop on poop, visit phred Tinseth's "phrannie" web site.
phred Tinseth © 1999-2002 Reproduction permitted

Make your own:

Many years ago when we needed one, there were no macerators made to fit an RV's holding tank outlet, so an old Hdyra-Flush, a 12-volt Jabsco marine macerator, and a PVC fitting from Home Depot were mated.

The pump is still operating fine (used it this morning) but the fuse holder and switch have been replaced. They use a lot of power and need HD wiring and switches. Power the pump using 12-gauge wire at a minimum (preferably 10-gauge) and add a 20-amp inline fuse.
DIY Macerator Pump

Get a pump that uses a garden hose instead of its own smaller diameter, short hose. The small hoses takes much longer to drain, easily kink and just are not long enough.

At home, we have a dedicated 50' 3/4" hose, for dumping-use only. The hose uses the washing machine's drain, in the garage. The hose end is equipped with a screw-on cap for securing it to the drain - helps prevents nasty surprises.
Drain hose connection

In the LD, we carry 65' of 5/8" dedicated drain hose. It's rolled up and stored inside the rear-mounted spare tire to keep it separated from the fresh water hoses. Also carried is a good size pipe wrench and a 3' cheater pipe used for opening home drain clean-outs. It gets used when driveway camping at friends or relatives. The cheater is also used when loosening and tightening lug nuts.
A dental pick is a good accessory to carry for removing things that gets wrapped around the impeller.
Our LD has a plug, located at the dump valve,power from an added-on switch panel.
Switch panel

For use on other RVs, a 25', 10-gauge extension cord, with alligator clips at one end, is used. The power is provided at the coach battery terminals.

This pump looks similar to our DIY pump and uses a garden hose.

Contributors: phred Tinseth, Larry Wade

Revised: 21 May 13

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