Tips for Choosing a 12V Replacement Water Pump

PART #2 OF 8

IS THE HYDRO-OBLITERATOR PUMP THE PROPER REPLACEMENT FOR MY OLD MEGA-WATERSLAYER PUMP?

That's a common question on websites, although more likely mentioning other pump brands. The answer is generally yes. Common aftermarket pumps are generally meant to be fairly universal replacements for OEM, and they all typically have the same plastic 1/2 inch x 14 MNPT (National Pipe Taper - male - 14 threads per inch) inlet/outlet like your OEM pump. (Note that the similar, but metallic, 1/2" fittings at Home Depot/Lowes may not have the same threads as the universal plastic connectors that come with new pumps, the latter available online via a search of "Shurflo NPT." But the "SharkBite" connectors at hardware stores MAY work.)

So you just need to ensure that your replacement pump has similar GPM flow (gal per min), comparable PSI pressure (pounds per square inch), and a compatible electrical fuse amperage. Compare the spec label on your OEM pump to the specs for a replacement, and also check your RV fuse box pump amperage as well. If your current pump is not original, don't assume the installer made the right pump choice. There may be a date of manufacture on your pump label that jives with your RV's model year, ensuring it’s OEM.

HOW MUCH FLOW?

Simply mimicking your OEM pump's specs is fine since you're deferring to the RV manufacturer. Otherwise Flojet suggests 1 GPM per water fixture (sink, shower, toilet, washer, etc.) under simultaneous use. If you just anticipate a sink and toilet operating at the same time, then a 2 GPM pump may suffice, although a higher flow pump won't be harmful, you simply won't fully utilize its capabilities. Flojet states that 1/2" barbed hose fittings (and therefore the entire water system) can flow up to 4.0 gpm. For yet more flow, one would presumably need to upgrade to 3/4" hose, with fittings that max out at 7.0 gpm, or eliminate all constricting "insertion" fittings such as barbed connectors, which all these flow numbers are based on. Lastly, 2.1 gpm max for 3/8" fittings. Being the smallest diameter part of the hose system, fittings are the limiting factor in regards to flow other than pump gpm rating.

PART #3 OF 8

HOW MUCH PRESSURE?

Prior to roughly 2000 many RVs used gray color polybutylene pipe, but it proved vulnerable to chlorine disinfectant in tap water. Since then the great majority of modern RVs now use durable PEX polyethylene piping, typically white, red or blue in color with a minimum 30 year lifespan and decent expansion to resist freezing damage. PEX is rated to 160 psi at 73 F (room temp) and 100 psi at 180 F (hot water). The actual burst point is closer to 400 psi for PEX in new condition. Since most pumps operate in the 30 to 55 psi range, your PEX plumbing is designed to withstand at least TWICE the pump pressure, a decent safety margin. Moving from a 45 psi OEM pump to a 55 psi aftermarket pump, for example, should generally not cause leaks or other problems, and is commonly done. Experts nonetheless suggest limiting pump pressure to 60 psi or less unless you have a need to go higher. The water fixtures in your RV have pressure limits as well, so it's not just about the pipe and fittings.

PUMP AMPERAGE

Flow (gpm) is more important than pressure (psi) for most RVs, especially with multiple water fixtures in simultaneous use. But pump amperage draw is largely dictated by flow. So going big on a pump flow rating can potentially overtax your pump's electrical circuit, and there's no need for a little teardrop trailer to have a 7 gpm mega-pump. As an example, Everflo pump max gpm/max amps draw for six of their pump models: 1.0 gpm/4.0 max amps, 2.2/8.0, 3.0/10.0, 4.0/13.0, 5.5/17.0, 7.0/23.0. (Their 3 gpm pump uses a max 10 amps, for example.) Notice how with these pumps if you double the flow (first number), you almost double the amperage (second number). I believe that many RVs come with 10 amp pump fuses/circuits, so you can see how going much above 3 gpm starts to become problematic. Therefore you might limit your choice of pump gpm to only what’s needed. And Flojet suggests 3 gpm equals three RV water fixtures in simultaneous use, and how many people exceed that? Note that other pump brands can have very different numbers than those above.

PART #4 OF 8

MADE IN CHINA

There's so many pumps to choose from, my poor German Shepherd suffered heart palpitations when I subcontracted the online research to him. Personally I'd avoid the weird Chinese brands on sites like Amazon – they have little or no brand name to protect. That said, Made in China is NOT the bugaboo many think it is since many Fortune 1000 firms manufacture premium products in their Chinese plants. The Uniroyal tires I put on my VW were made by Michelin in their Chinese plant, and were absolutely the equal of any Michelin tire made in their U.S. plants. Corporate and ISO quality standards/audits help ensure that. On the other hand, a water pump engineered AND made AND sold by a Chinese firm, well that's problematic for me. Bottom line: You're NOT buying a country of manufacture. You're buying a brand name, or lack of same, and everything that brand name represents. Made in China is NOT a quality problem – it's WHO makes it in China that matters. Fortune 1000 firms routinely make first-rate products in their Chinese plants. But Chinese companies? Well, typically not so much...

SO WHICH PUMP?

So what brand and pump model to buy? There's lovers and haters for every pump model available, and you can wade into that deep end of the pool if you like via the Amazon buyer reviews. Rather than a subjective "Best water pump" thread, I'll stick to generalities here and comment on several U.S. brands and the reliability that suggests. (Sorry, Seaflo, a Chinese firm.)

Pumps I would suggest considering, in random order, include the Lippert Flow Max, the Valterra HydroMax (both Lippert and Valterra are large OEM parts suppliers to the RV industry), Shurflo pumps (various part numbers), and Flojet pumps (various). These are all established U.S. brands with generally good reputations. There’s a few other U.S. brands as well, but they’re less common.

PART #5 OF 8

JUST PICK ONE FOR DOG'S SAKE

If you're ultimately confused or overwhelmed by the choices, I might simply recommend either a Valterra or Lippert pump, both good choices. Not because they're better than the competition – they're likely not – but simply because both firms offer only a single, one-size-fits-all, semi-universal 12 volt RV/boat pump. So an easy choice! The Shurflo and Flojet pumps are good too, and they both offer various pump models. Choosing from these four below based on lowest price is not a bad approach. If you're into preventive repairs and stumble across a fire sale price in an Ebay auction, and your pump is 10 years old, you might consider a PREVENTIVE replacement so a future vacation isn't ruined. Feel free to disagree – that's admittedly a subjective idea from me, and my Shurflo did last a long 16 years.

Regarding the data below, note that pump labels and manufacturers' literature sometimes have modestly conflicting data, especially regarding psi and RV fuse amperage. I suggest using the pump motor label as the "bible."

VALTERRA HYDROMAX
-One pump model offered
-3.0 gpm flow
-55 psi max pressure
-7.5 amps max draw
-10 amps or higher RV pump fuse required
-Bypass valve to reduce cycling and pulsation
-Plumbing strainer and connectors provided
-Can run dry without damage
-2 year warranty

LIPPERT FLOW MAX
-One pump model offered, although specs can modestly vary
-3.0 gpm flow
-50 psi max pressure
-8 to 9.5 amps max draw
-10 amps or higher RV pump fuse required
-Note that Lippert variation #DS-01230-D2 may state a 15 amp fuse, deferring to an unstated electrical code. But all Lippert pumps appear to use no more than 9.5 amps, and many of their 9.5 amp pumps explicitly call for a 10 amp RV fuse. Therefore it appears that ANY Lippert pump can likely get by with a common 10 amp RV fuse, even if it says “15 amp fuse” on the pump label.
-Plumbing strainer and connectors provided
-5/10 minute duty cycle – 5 min full flow, 10 min cooldown (see below)
-Designed to survive freezing
-Can run dry without damage
-2 year warranty

FLOJET
-Several pump models available
-Pump #R3526144D (or #03526-144) is popular
-2.9 gpm flow
-50 psi max pressure
-5.2 to 7.5 amps max draw
-10 amps or higher RV pump fuse required
-Bypass valve to reduce cycling and pulsation
-Plumbing strainer and connectors provided, proprietary o-ring style
-Unique 58 mm x 81 mm mounting hole spacing
-Can run dry without damage
-2 year warranty

SHURFLO
-Several pump models available
-Pump #4008-101-A65 is popular
-A65 suffix is OEM, E65 suffix is aftermarket, same pump
-3.0 gpm flow
-55 psi max pressure
-7.5 amps max draw
-10 amps or higher RV pump fuse required
-Bypass valve to reduce cycling and pulsation
-No plumbing strainer or connectors provided, so extra $$, search online for “Shurflo NPT”
-Can mount in any position including motor down
-Can run dry without damage
-2 year warranty

PART #6 OF 8

SOME PUMPALICIOUS NOTES

In addition to the mainstream pumps above, there’s beefier and pricier pumps available such as the Jabsco and Remco brands, often used on boats but applicable for RVs as well. (Trivia: Boats can be thought of as waterborne motorhomes and they share many components. But boat components and installations tend to be more robust than RVs, and for a simple reason. If stuck on the highway outside Yellowstone you can call AAA for help. But a boat component failing 100 miles from shore in a squall is much more serious.) Unlike other brands, Shurflos generally don't come with a strainer (it’s just a debris strainer, not a true filter) or selection of connector fittings, so you may need to reuse your old fittings if possible or buy those separately, about $8 each online via universal “Shurflo NPT” fittings you can use with almost any brand of pump (fittings generally not found in Home Depot and Lowes stores). And Flojets have unique proprietary fittings with internal o-rings (similar to BMW cooling systems), although that won't be a complication for most people – they'll hook right up to your current plumbing. The Lippert pump has a 5/10 duty cycle. That means you can substantially flow water through it for a continuous 5 minutes, but then need to let it rest and cool down for 10 minutes before resuming water use. For most folks I suspect that would only be an issue if showering, unless you have a mega RV. RV pumps are generally engineered for intermittent use rather than continuous use like industrial pumps. They'll get hot if overtaxed, and may shut off until cooled sufficiently to automatically reset via their thermal sensor (180 F overheat shutoff temp for Remco, for example). And should you see a little water leak from your pump right out of the box, rather than a "used pump" scenario, that's likely just from post-assembly factory pump testing. Some people freak out about that water, assuming “used, returned, resold,” and it shows up in Amazon negative reviews.

PART #7 OF 8

ANTI-NOISE INSTALLATION TIPS

For each pump listed above you can find Amazon reviews that say “Quiet pump!” AND “Noisy pump!” So I won’t even go there and try to referee all that, it’s subjective and pointless, and much noise comes from the installation and plumbing anyway. All pumps come with rubberized bases to reduce vibration and noise. Their four-screw mounting hole spacing appears fairly consistent amongst brands, generally a 73 mm by 83 mm (2-7/8" by 3-1/4") rectangle (oddly 58 mm x 81 mm for Flojet). The Shurflo #2088 pumps commonly used as OEM have 76 mm x 83 mm hole spacing, but you can reuse those holes by simply tilting the screws a bit while inserting -- the difference is only 3 mm total, or 1.5 mm per screw. Measure your new pump's feet to get an idea of proper screw length and buy new screws to reduce the likelihood of complications. Your installation may differ, but a #8 wood screw 1.25" long is a good starting point, or 1.5" if you insert a mouse pad or similar under the pump feet. You might buy 1", 1.25" and 1.5" #8 wood screws and return what you don't use. Otherwise just use a drill or nail to make new holes if the prior holes don't work; Shurflo recommends lightweight #8 diameter screws (thicker screws actually transfer more noise to the board), and do not overtighten them, which may compress the rubber and therefore increase noise transmission to the plywood or other base. A solid base is best – a lesser, thinner base that sounds like a drum when tapped can transmit noise. Inserting a small patch of carpet, mouse pad or felt pads for furniture legs between the pump’s base and mounting board can help, or perhaps a hardware store has supplemental rubber washers, bushings or such that can help, although all of that may be overkill. In one forum thread an installer ran his new pump, with rubber feet on the plywood, and noted the noise. Then he lifted it up in the air, off the plywood, and the noise did not change. This suggests that noise is much more from piping than from rubberized feet on a new pump, with little need to “improve” manufacturers’ pump mounts.

RV water pumps shouldn't be connected directly to rigid piping since doing so will transmit vibrations, and therefore noise, throughout the plumbing system and RV. It can also invite pipe cracking and joint loosening. Instead you should install at least 12 inches (Lippert says 12" min, Shurflo says 18" min) of flexible hose at both the pump inlet and outlet to absorb that vibration rather than transmit it. If your old flex hose has stiffened, you might replace it. You can even install a pre-made 36 inch long flex hose "silencing kit" at the pump inlet and outlet, with each hose curved into a big, wacky, loose loop (like a water rollercoaster!) if space permits, to help reduce noise, and such hose loops are actually recommended by Flojet. Google "Xylem FloJet 3426 Series Manual - ManualsLib" for an image of the installed loops, or view the photo below. See Shurflo #94-591-01, Camco #20105, and Valterra #P23512PB universal hose silencing kits (see Amazon reviews before considering the RecPro equivalent). Also see Shurflo #411-010-00, 411-020-00 and 411-030-00 for other universal silencing hose options. Or you can use bulk generic hose – see Eastman/EZ-Flo #98628 or by-the-foot EBay options, ½” ID and ¾” OD (inner/outer diameters) of reinforced hose made of vinyl/PVC/polyvinyl chloride, their thickwall ¾” outer diameter helping to prevent hose kinking. Search terms are “1/2 vinyl reinforced tubing,” with tubing the proper term rather than hose. The various “silencing kit” hoses are safe for RV drinking water, but for generic bulk hose look for ANY of "potable/food grade/non-toxic/FDA compliant/NSF51/NSF61." (51 is safe for foods and beverages such as milk and beer, 61 is specific to potable water, but either is sufficient for RV freshwater. Since vinyl MAY impart a taste in water when stored, it’s possible that 61 is unattainable for vinyl flex hose, the taste issue failing the standard even though safe.) Don’t buy standard (non-reinforced) clear vinyl hose rated at 30 psi, but look for reinforced vinyl hose with the polyester white stringy thingies (NOT embedded worms!) rated at 150 psi. For 3/4" OD hose it's best to use hose clamps that max out at 7/8" or 1" diameter such as the Ideal #670040008018, Apollo #IDL16 or Everbilt #6760595. If using larger clamps and tightening them down to 3/4" they have a tendency to compress into ovals with sharp angles, which you'll want to flatten out into a smooth circle with a pair of pliers. Better to just use a properly sized smaller clamp to avoid complications or leaks. Avoid 90 degree elbow fittings close to the pump’s outlet port, although sometimes they’re unavoidable. They cause turbulent water flow and also back pressure, both of which generate noise. Use smooth curves rather than right angle bends where possible.

PART #8 OF 8

ANTI-NOISE INSTALLATION TIPS CONTINUED

If frequent pump cycling or pulsing noise is problematic, a small, $30 to $60 accumulator tank can be added, but most installations won't require that, and most RVs don’t have them. These softball-sized tanks have a small air bladder inside that acts like a balloon, with both water and trapped air in the tank. The water won’t compress, but the air does, so with each pump pulse the trapped air briefly compresses, acting as a hydraulic shock absorber for the overall water system, reducing water hammer, noise and pump cycling. They can significantly help for problematic systems, a simple installation with two inlet/outlet nipples plus mounting feet. They make larger accumulator tanks as well, and due to their stored pressure they can even flow a little water without the pump running, so you can silently get a glass of water or flush the toilet at midnight without the pump cycling. A pump bypass valve is an internal spring-loaded diaphragm that opens up allowing water from the discharge side back to the inlet side of the pump, smoothing water flow and helping reduce cycling and pulsation. Both Shurflo and Flojet claim that pumps with bypass valves reduce or negate the need for an accumulator tank. The Lippert literature doesn't mention a bypass valve, but the Valterra, Shurflo and Flojet pumps all have bypass valves.

These eight posts cover mainstream constant speed pumps. More expensive variable speed water pumps (not covered here) are able to deal with water flow and pressure changes more smoothly, and negate the need/benefit of an accumulator tank.

Also check for pipes or hoses transmitting noise through contact against walls and such. Foam pads can be inserted in spots to reduce contact noise transmission. Pumps typically have pressure switch/bypass valve adjustment screws to reduce cycling, pulsing, and therefore noise, but the factory settings should work well for most people – read the manual. As for Teflon tape, I suspect the basic rule is to NOT use it since stray bits of tape can enter the pump or a water fixture and cause problems. But if a connector leak is persistent, then USE tape if you must to resolve. Some hose connectors have visible soft internal sealing gaskets, some have no gaskets (just smooth plastic mating against smooth plastic), both are common and workable. You might inspect your fittings’ mating surfaces for significant imperfections before installation, and gently try to correct if needed. Check for leaks after final installation, of course…some fittings are more equal than others. If mounted on a wall, the pump motor should face up so a potential pump leak doesn't flow from the pump module down into the motor (Shurflo #4008 can be mounted in any position). If you’re worried about freezing, the Lippert pump is rated to five freeze cycles, but I did not find any freezing references in other pumps’ literature or manuals. Pump documents commonly mention run-dry survivability should the tank empty, so that design feature appears more anticipated and common ("2 minute" run-dry protection in a Shurflo document from 2013, so perhaps that's a rough industry standard?). You might read through the entirety of a pump owner’s manual before buying, such as through a Google search of “Flojet 12 volt water pump manual,” and also search for a photo of a pump’s motor label via Google Images. The Lippert pump, for example, mentions a 5/10 duty cycle on their motor label, but nowhere in their various literature, catching shower users by surprise after purchase and installation.

So, lots of pumpy electronic word thingies there. Hope this is helpful! I have to go console my German Shepherd now...

Image of pump inlet and outlet hose loops similar to manufacturers' hose "silencing kits," two 36 inch long hoses per kit. Explicitly recommended in Flojet pump owner's manuals. If 36 inches of loop is not feasible, try for 12 to 18 inch straight sections of flex hose, both inlet and outlet. Silver component is the pump, black component appears to be an optional accumulator tank.

An elegantly simple pair of noise/pulse reduction loops to dissipate vibrations. The 90 degree elbow on the pump's outlet port is not optimal, but may be necessary due to space limitations.

Why do we need 8 post from someone who's not an expert about water pumps? :D