A macerator pump grinds tank waste fine enough to push it through a garden hose, so you can dump uphill, across a long run or into a home sewer cleanout where a gravity hose cannot reach. The trade is speed: the higher and longer the run, the slower the dump.
RV Macerator Pumps: When You Need One, Flow, Lift and Distance
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At a glance
- What it does: Flojet's portable macerator chops waste to 1/8 in maximum so it can be pumped through a garden hose instead of a 3 in sewer hose.
- How far: Flojet rates its pump for 150 ft horizontally through 3/4 in hose, and Thetford says not to extend its discharge hose beyond 150 ft.
- The cost of distance: Thetford's own chart falls from 18.7 gal/min on the stock hose to 0.7 gal/min at 9 ft of height through 100 ft of garden hose.
On this page (7)
What a macerator pump does
It empties the tanks without relying on gravity. It is a 12 V pump with a cutter on its inlet, and Thetford says it handles human waste and toilet tissue, so one pump does black and gray water.
A macerating toilet is a different product, covered with the other RV toilet types.
Do you need one?
Only if gravity cannot get the waste there. If the inlet sits below your dump valve and within reach, a plain gravity sewer hose needs no power and has nothing to jam. A pump earns its place when:
- The sewer inlet or cleanout is uphill from the RV.
- The connection is far from the rig, or across ground you cannot drag a 3 in hose over.
- You want to dump at home into a sewer cleanout, where only a garden hose will fit.
A built-in pump still needs gravity on its inlet side: Thetford requires the pump to sit below the holding tank, and recommends a licensed tradesperson for the plumbing and electrical work on a retrofit.
Portable or built in
A built-in unit stays plumbed to the RV; a portable one twists onto the dump valve when you need it. The Sani-Con Turbo 300 ships with a 3 in bayonet adapter, a 1.5 in discharge hose and alligator clips on a 35 A fuse holder.
The Flojet 18555000 is the portable pattern: a 3 in inlet that replaces the sewer hose, a garden hose discharge port, a fresh water inlet to rinse the pump and a handheld switch. Flojet warns not to mount it permanently to the RV waste port.
Shurflo's 3200 and Jabsco's 18590 are inline pumps plumbed into the system; Jabsco's manual presents the 18590 for marine holding tanks and does not mention RVs.
How far and how high it pumps
Every foot of height and hose slows the dump. Thetford's chart for the Sani-Con Turbo shows how much.
| Hose | Height | Flow |
|---|---|---|
| Stock 1.5 in, 21 ft | 0 | 18.7 gal/min |
| Stock 1.5 in, 21 ft | 9 ft | 11.1 gal/min |
| Plus 50 ft garden hose | 0 | 6.2 gal/min |
| Plus 100 ft garden hose | 0 | 3.7 gal/min |
| Plus 100 ft garden hose | 9 ft | 0.7 gal/min |
Figures from the Thetford Sani-Con Turbo 700 owner's manual. At 0.7 gal/min, 100 gallons takes Thetford's quoted 143 minutes, so the far end of the chart is a last resort.
| Pump | Flow the maker prints | Distance or height |
|---|---|---|
| Thetford Sani-Con Turbo | 18.7 gal/min on its own hose | Do not extend beyond 150 ft |
| Flojet 18555000 portable | 11 gal/min max at 12 V; 7.0 gal/min through 100 ft of 3/4 in hose | 150 ft horizontally |
| Shurflo 3200, RV and marine inline | 13 gal/min at 0 ft head | Max operating head 30 ft |
| Jabsco 18590, marine inline | 12.5 gal/min at 0 ft, 7.5 gal/min at 20 ft | Head figures given to 20 ft |
Sources: the manuals above, the Shurflo 3200 manual and the Jabsco 18590 manual. Flojet notes that longer runs raise resistance and may overheat the motor.
Tip: Thetford's built-in discharge hose is 1.5 in, and an extension must be a garden hose of 0.75 in inner diameter or greater to avoid pump failure.
The downsides makers name
A macerator needs more care than a gravity hose.
Never run it dry. Thetford says not to at all; Flojet and Jabsco allow no more than 30 seconds, Shurflo 15 to 20 seconds. The cue is the pump turning louder and higher pitched as the tank empties.
Nothing that does not dissolve. Thetford allows only human waste and toilet tissue, and says items such as wet wipes or paper towels will damage the macerator and void the warranty.
Short runs only. These are intermittent-duty pumps: Flojet allows 30 minutes continuous, and Thetford's manuals give 15 to 20 minutes before the thermal cut-off trips. When it stops, let it cool.
Its own fused circuit. Each maker specifies a dedicated 12 V supply:
- Thetford Sani-Con Turbo: 35 A breaker or fuse.
- Flojet 18555000: 20 A fuse in the handheld control.
- Shurflo 3200: 17 A maximum, 25 A fuse recommended.
- Jabsco 18590: 20 A draw, 25 A fuse.
Rinse and drain after use. Thetford has you empty the black tank first and rinse with gray water, drain the hose completely before storing, and never leave the unit pumping unattended. Jayco warns to check the hose is connected at both ends before switching on, because the hose is pressurized.
Tip: Find the bypass before you need it. Jayco's macerator bypass valve lets the tanks gravity dump to a 3 in sewer connection if the motor fails. Water also sits in the hose and macerator box, so winterize them with the rest of the plumbing.
Dumping at home
Your city or county decides whether you may dump at home. Flojet says the pump can empty the holding tank into a sewer cleanout at your home, used in line with EPA sanitation regulations. The City of El Cajon, California allows it with proper equipment; Los Angeles County does not allow connecting to an existing cleanout for RVs used as temporary housing.
On a septic system, read the EPA's alert for RV owners: chemicals in some tank deodorizers can pass through to soil and ground water and corrode system parts.
Common questions
What does a macerator pump do on an RV?
It empties the black and gray tanks under pressure instead of by gravity. Thetford's chart for the Sani-Con Turbo tops out at 18.7 gal/min on its stock hose.
What are the downsides of a macerator pump?
More upkeep than a gravity hose, and a slower dump once you add height or a long garden hose.
How far can an RV macerator pump push waste?
Flojet and Thetford both give 150 ft on the flat. Height cuts flow sharply, so a long uphill run will be slow.
Can I dump my RV tank into a home sewer cleanout?
Often, but it depends on where you live. Ask your city or county before the first time.