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Old 10-08-2007, 08:59 PM   #29
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Alpine Owners Club
Join Date: Aug 2007
Location: Long Beach, CA
Posts: 1,563
Well, it's finally complete. I now have access to every last drop in my water tank.

1) I stopped the siphoning, as per the last post.

2) I re-seated the tank so that the main drain valve wasn't caught on the steel frame (causing the bottom to bulge upward).

3) Removed the pump inlet line from the rear sid of the tank and plugged the hole.

4) Installed a tee at the main drain, above the slide valve (with the cable release handle) to send water to the pump. I used a bit of ABS and PVC along with the 1/2" waterline and some insulated straps to attach the line to the rail (away from stored items).

Boy, it's tight in there! I also found the slide control/sensor unit down in there, complete with several 10 amp AT fuses (see bottom of pictures). Here're the pictures:

Next, can anyone suggest a quieter pump? Maybe the Shurflo 5.7 variable?

2003 Alpine 40FDTS (400HP)
Long Beach, CA
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Old 10-09-2007, 08:17 AM   #30
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Alpine Owners Club
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Location: Oregon
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One good thing about a water pump that makes a little noise is if you have a leak in the system you may hear it before you loose all your water. Very annoying when when your dry camping.

05 Alpine 36MDDS, 09 Subaru Forester, no animals.
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Old 10-09-2007, 12:35 PM   #31
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The 5.7 on my 06 was quieter than the diaphragm type we had on the Trek (which was loud by my standards). The 08 mounting is way quiet. So quiet in fact, I left the City/Fill valve switched to Fill and the pump on, and I didn't hear it till about 3 hours later (pump ran the whole time) (twice). Now I hafta remember to switch it back, and that system doesn't work as well as it used to.
Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project
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Old 10-09-2007, 03:06 PM   #32
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Does your '08 use the Shurflo 5.7? I tried to check online, but they are still touting the '06's as their latest and greatest. That poor website is a joke!

I just received a bunch of eLiterature on quieting the pumps from Shurflo. They cover installation and the silencing kit. It all makes sense.

From Shurflo: The silencing kit is available to address the hard plumbing that may currently be attached directly to the pump. This can amplify noise and create vibration where the tubing flexes and absorbs some of the noise. The silencing kit is basically (2) pieces of 30" soft tubing with connectors on each end. I have attached service bulletins that addresses this subject.

Noise reduction may be improved by following a few simple guidelines when installing the pump.

A) Mount the pump on a solid structure. If you mount the pump to a structure that flexes (no matter how small) it WILL ACT as a "sounding board" and actually amplify the sound.
B) DO NOT over tighten the four mounting screws in the rubber feet of the motor. DO NOT crush down the rubber mounting pads more than .030 (1/32") to .062 (1/16").
C) Use ONLY flexible tubing for at least the first two feet on both the inlet and outlet sides of the pump head. If you use rigid tubing or hard plastic, the pump vibrations may be amplified throughout your plumbing system

A Discussion on Recreational Vehicle Plumbing System Noise

Positive displacement pump "noise" can be attributed to many factors. The simple way that the pump operates lends itself to some kind of noise. A rotating motor shaft is connected to a cam, which rotates and drives a diaphragm up and down in three separate chambers. These chambers draw water in on the down stroke of the diaphragm and seal shut on the diaphragm upstroke, which also pushes water out through the outlet valve and past the check valve. In a motor that operates at 1800 rpm, that's 10,800 valve cycles and 10,800 diaphragm flexes per minute. This does not even take into account water turbulence, motor bearing rotation and brush contact. Our goal is to reduce the amount of this noise transmitted in a motorhome.

Mounting on a Solid Surface
Pump should be mounted on a solid surface, with solid supports underneath the mounting surface. If you can knock on the mounting surface and it sounds like a drum, vibrations are doing to travel through it.

Rubber Mounting Feet
SHURflo supplied rubber feet should be used to mount the pump to the mounting surface. Mounting screws should not be oversized, and should never be tightened too tight. Flattening out the mounting feet reduces their ability to isolate vibration. The manual calls out #8 screws, #6 would be better yet.

Flexible Tubing
At least 18" of high pressure flexible tubing should be used between the pump and "hard" plumbing both on the inlet and outlet fittings. The use of this tubing reduces vibration transferred from the pump through the rest of the plumbing system.

Fittings & Piping
Elbow fittings should be reduced to a minimum near the outlet ports of any pump. Elbows cause turbulent flow and back pressure on the pump. Both of these conditions can cause noise.
Another cause of plumbing system noise can be the vibration of the piping and fittings against the walls of the motorhome. Common places for this type of noise are the holes where plumbing goes through walls and behind drawers and shower walls, but can occur anywhere in the system.

Checking an Existing RV Plumbing System for Noise

 Knock on the mounting surface in several different places. Does it sound like a drum? Sometimes a little foam padding or carpet beneath the pump can reduce this problem.
 Check the mounting screws. Do they look oversized? Do they look too tight?
 Bleed all air out of the system, including all drain lines, while the pump is on. Excessive air can cause plumbing to hammer and rattle.
 Grab the piping on either side of the pump. Does the vibration seem excessive? Does the noise and vibration level decrease while you hold the piping?
 Are there a lot of elbows within the first foot or two of the pump outlet? Would the use of some high pressure flexible tubing eliminate some of those elbows?
 Turn on fixtures on at a time. Does the system make more or less noise when any of these are used? Use this method to track excessive noise and vibration.
 Check the flow into the pump. Clogged strainers in the tank or at the pump, as well as air leaks can make the pump labor and cause noise.
 Refer to the SHURflo potable water installation


Is your pump cycling excessively? Common correctable causes of excessive pump cycling are flow restrictors. Flow restrictors work on the principle that if there is a smaller hole, less water will come out. While this is true, back pressures build up on the pump, causing it to cycle and give erratic water flow. Flow restrictors are generally found in faucets and shower heads. Removal of these flow restrictors can reduce or eliminate pump cycling problems.


Unscrew the faucet nozzle and examine the inside. The flow restrictors
usually located between a gasket and a particle screen. It looks like a circular
disk with a small hole in the center. Remove the flow restrictor and replace
the screen and gasket. Be sure to clean the screen if it is dirty. The flow
restrictor may be a part of the aerator assembly. If it is, carefully pry out
the flow restrictor from the assembly, and replace the aerator, screen
and gasket. Replace the faucet nozzle, and you're ready to go.


There are usually 2 types of shower head flow restrictors: the disk-type, similar to the faucet flow restrictor, and an integral "low-flow" ball socket flow restrictor.


Disk-type flow restrictors are usually located between the shower
Head and the hose line. Simply unscrew the head, remove the flow
Restrictor, and replace the head. Be sure to clean and replace
Any gaskets and screens.


Ball socket flow restrictors need to be removed and have a
Larger (1/4") hole drilled in them to allow more flow. Be
Careful while doing this. Simply disassemble the shower
Head, drill a " flow hole, clean up any debris, and
Reassemble the shower head.

Please refer to the SHURflo Service Manual 911-124, page 4, OUTLET PLULMBING, for more information on other causes of excessive pump cycling.

Hope this helps someone out there!
2003 Alpine 40FDTS (400HP)
Long Beach, CA
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Old 10-09-2007, 07:22 PM   #33
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Posts: 5,263
Yes, 5.7, same pump as the 06. Mounting is different in the 08 and I think that is the difference (drop) in noise so there must be something to that mounting info you posted.

Baja-tested '08 2-slide 36'
Alpine: The Ultimate DIY'er Project
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