Installing a new SureFlo water pump...

[Pete Masterson]

The typical pressure with city water is about 45 psi inside the coach. The fill system (at least on the later 'birds) has a built in pressure limiter that holds to about that maximum.

Water pressure in most city systems is at least 65 psi and can be well over 100 psi. (The water pressure at my home is about 90-95 psi most of the time.)

The first thing to do is get yourself a water pressure gauge. Home centers often have then with a female hose-fitting coupling. I installed a hose-thread end on my outside faucet, replacing the original aerator end. (Home center again.) You can put the hose thread on most faucets with the simple conversion kits available at most home centers. (These were originally designed to help folks fill water beds...) Then you can screw on the water pressure gauge and check the pressure at that point. Then you'll know where you're starting.

The plumbing in my RV is similar to plumbing used in regular homes built at about the same time. Unfortunately, the type of plastic pipe used did not have the life expectancy under full city-water pressure and it was eventually recalled from that service and is no longer on the market. However, it has not shown any signs of difficulty dealing with the 65 psi provided by the 5.7 gpm variable speed pump. 

The pump cycles on when its internal sensor detects a drop in water pressure, then it matches speed to the demand for water, holding the pressure relatively constant. When a faucet is turned off, then the pressure goes up slightly and trips the pump to slow down or shut off. 

The variable speed pump does not require the accumulator tank. The accumulator tank helps a single speed pump by buffering the pump output as it cycles on and off to supply the demand. For example, say you have a 4 gpm pump that operates with 45 psi. When you open a faucet the pressure is first provided by the accumulator tank as the internal rubber diaphragm presses against the water. The pump will sense the lowered pressure and will then run at full speed until either the accumulator tank is repressurized or as long as the pressure is below the set point. When you close the valve, the pump will continue to run until the accumulator tank is back to the set level (usually about 45 psi).

If you attach the accumulator tank with a variable speed pump, you'll not have any particular advantage and the pump might actually run longer to bring the accumulator tank back up to pressure when you open a valve. Since the variable speed pump starts within a fraction of a second when the pressure drops, you won't ever notice any lag to your water pressure and the variable speed pump matches your needs quite well. Indeed, without the accumulator tank, hearing the water pump cycle (when there is no water being used) is a sure sign that there's a minor leak somewhere. If the accumulator tank is installed, you might never be absolutely sure when you hear the pump cycle with all valves closed if it's just topping up the accumulator tank or not. Anyway, removing the accumulator tank simplifies the plumbing.

If you do install the variable speed pump, be sure to mount it with sound deadening in mind. It has rubber grommets in the mount  --- but attaching it to a solid piece of wood, well anchored to the coach, is likely to reduce the noise transmitted through the structure by the vibrations of the pump. My pump is attached to a bulkhead in one of the basement compartments. I can hear it when it cycles, but it is not particularly intrusive. (e.g. when someone uses the toilet in the night, it doesn't wake everyone up). However, if the pump is located under your bed (as in some of the earlier coaches), then more consideration of mounting to reduce noise transmission will probably be more important.

I can't say right out that the 65 psi won't be a problem, but the concern for RV plumbing handling too much pressure goes back to the early days when tanks were pressurized to provide water pressure (as I recall from 1966 or so). While RV plumbing goes through more severe service issues than does plumbing in a home, 65psi isn't generally a major concern in most RVs. If your coach has copper plumbing throughout, then you're probably ok for 65 psi or much higher. 

I note that PPL has the Shurflo 5.7 Variable speed on sale. See:

<http://www.pplmotorhomes.com/parts/rv-pu...r-pump.htm>

Shurflo also offers a 4 gpm variable speed that only goes to 50 psi. See:

<http://www.shurflo.com/pages/RV/rv_categ...treme.html>

for details. Both pumps are linked to this URL at the manufacturer's web site.

I note that the 5.7 pump seems to be the more popular (or, at least, the most heavily promoted). The 5.7 seems to be widely available, but I didn't notice the 4.0 gpm variable speed pump offered as frequently.

Note: if you get either of these pumps, you'll also need a new screen/filter rated to work with the pump. Don't forget to order one at the same time.

Pete Masterson

'95 Blue Bird Wanderlodge WBDA 42

El Sobrante CA

"aeonix1@mac.com"

On Jul 2, 2008, at 3:03 PM, Ryan Wright wrote:

Just need some advice on size, etc. I like the 5.7 variable speed

pump, but is 65psi excessive? Am I looking to get myself into all

manner of plumbing problems brought on by the pressure?

I only need the pump to match the pressure I get when hooked up to

city water. Showers are great when I have city water hooked up.

Terrible with my current water pump.

Another question, I'd like to keep the factory pressure tank so the

pump runs less often. Will the Sureflo 5.7 eat it up, or will they

work OK together?

Thanks in advance for any advice.

-Ryan

'86 PT-40 8V92

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