12 volt water pump: flow you can feel, amps your battery can spare
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Quick answer
A 12 volt demand pump pressurizes an RV, cabin or off-grid tank system and switches on when you open a tap. Pentair's SHURflo Revolution 4008 lists 3 gallons per minute, 55 psi shut-off and 7.5 amps maximum; the 4048 High Flow lists 4 gallons per minute at 10 amps. Pick the flow your fixtures need, then check that the battery can supply the current. Both list thermal protection and say they can run dry without damage.
Two SHURflo pumps compared
| Spec | Revolution 4008-101-E65 | 4048-153-E75 High Flow |
|---|---|---|
| Voltage | 12 VDC | 12 VDC |
| Flow | 3.0 GPM (11.4 LPM) | 4.0 GPM (15 LPM) |
| Max amps | 7.5 A | 10 A |
| Shut-off pressure | 55 psi | 55 psi |
| Dimensions | 8.1 x 4.9 x 4.3 in | 10.3 x 4.9 x 4.8 in |
| Bypass | Internal | Internal, with Flow Reaction Technology to reduce cycling |
| Priming | Self-priming | Self-priming to 6 vertical feet |
| Run dry | Yes, thermally protected | Yes, thermally protected |
Pentair also lists a 24 volt 4008 version at 4 amps and a 115 volt AC version at 1 amp, for systems that are not 12 volt.
How much flow you need
- Start from your fixtures: add up the flow of the taps and shower you expect to run at the same time and compare it with the pump's rating.
- More headroom: the 4048's 4 GPM is a third more flow than the 4008's 3 GPM.
- Pressure: both shut off at 55 psi; the pump switches on again when you open a tap and pressure drops.
- Cycling: Pentair says the 4048's Flow Reaction Technology reduces rapid cycling.
Amps and battery draw
- Max watts: 7.5 A x 12 V is 90 W for the 4008; 10 A x 12 V is 120 W for the 4048.
- Daily energy, upper bound: running 10 minutes a day at maximum current uses about 1.25 Ah on the 4008 and about 1.67 Ah on the 4048.
- Real use is lower: a demand pump runs only while water flows, so most days use far less than the maximum.
- Battery bank: see our RV battery and 12 volt lithium battery guides for sizing the bank that also runs lights and fans.
Tank, pump and battery together
A worked example with a 50 gallon fresh water tank, an example size:
- Emptying time at full flow: about 17 minutes of continuous running for the 4008 at 3 GPM, or 12.5 minutes for the 4048 at 4 GPM.
- Battery for the whole tank: at maximum current that is about 2.1 Ah either way, because the faster pump draws more current for less time.
- What decides it: tank size, not the pump, mostly limits how long you have water; the pump choice decides how strong the flow feels.
Pentair also makes the 4008 in 24 volt (4 A) and 115 volt AC (1 A) versions; match the pump voltage to your system rather than adapting it.
Installation: follow the manual
- Mounting: Pentair says both pumps mount in any position.
- Strainer and check valve: the 4048 has a built-in check valve to prevent backflow; follow the manual for inlet strainers and fittings.
- Wiring and fusing: use the wire size, fuse and switch the pump manual specifies, or have a qualified RV technician install it. We do not give wiring steps here.
- Replacement: Pentair says the 4048 replaces its older 4900 and 5900 Smart Sensor pumps; match fittings when swapping.
Priming, running dry and winter
- Priming: the 4048 self-primes to 6 vertical feet, so mount the pump within that height of the tank outlet.
- Running dry: both pumps list thermal protection and say they can run dry without damage, useful when a tank empties unnoticed; still switch the pump off when the tank is empty.
- Freezing: drain or winterize the system before freezing weather; Pentair sells a winterizing system for its RV pumps.
- Water quality: a pump moves water, it does not treat it; see our water storage tank and water purification tablets guides.
What to look for when you buy
Standard RV pump: SHURflo Revolution 4008-101-E65
Best for: Small RVs, campers and cabins running one fixture at a time
Pentair lists 12 VDC, 3.0 GPM, 55 psi shut-off, 7.5 A maximum, automatic demand, quiet operation, thermal protection, dry-run tolerance and any-position mounting.
Watch out: Lower flow when two fixtures run together.
See options on Amazon (opens Amazon in a new tab)Higher flow: SHURflo 4048-153-E75 High Flow
Best for: Larger RVs and cabins with two fixtures running at once
Pentair lists 12 VDC, 4.0 GPM, 55 psi, 10 A maximum, reduced cycling with Flow Reaction Technology, self-priming to 6 vertical feet and a built-in check valve.
Watch out: Draws more current and is 10.3 in long; check space and fuse size per the manual.
See options on Amazon (opens Amazon in a new tab)Questions people ask
- How many amps does a 12 volt water pump draw?
- Pentair lists 7.5 A maximum for the SHURflo 4008 and 10 A for the 4048; demand pumps run only while water flows.
- How do you prime a 12 volt water pump?
- Self-priming pumps pull water from the tank when switched on; the 4048 self-primes to 6 vertical feet. Follow the manual.
- Can a 12 volt water pump run dry?
- Pentair says both SHURflo pumps can run dry without damage and are thermally protected.
- How do I wire a 12 volt water pump?
- Use the wire, fuse and switch the pump's manual specifies, or have a qualified RV technician install it.
Sources
- Shurflo Revolution 4008 Series By-Pass Pump, Pentair
- Shurflo 4048 High Flow Pump, Pentair