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Water System Expansion Tank
   Netboy’s water system summary cannot possibly be improved on. So here it

   “Most RV water pumps are the "demand" type. Whenever you turn on a
faucet, the pressure switch on the pump senses the drop in pressure and turns
on the pump. As soon as you turn off the faucet, the pump's pressure switch
senses the rise in pressure and shuts off the pump.  This type of system works
fine, but the pump is often irritatingly noisy, and the pump gets turned on and
off many times (each time a faucet is turned on or off) which can shorten the
pump life.  Adding a small water storage tank to the system, called an
accumulator, reduces noise and pump cycling. An RV water system
accumulator tank typically has a water inlet at one end, an air-fill valve at the
other end, and a flexible rubber or vinyl bladder separating the air and water.
The tank is installed by tee'ing it into the piping on the discharge side of the
pump. In use, the tank provides a pressurized air cushion over stored water.
The idea is that once your pump comes on (say at 30 psi), it will pump water
into the accumulator tank, and that water compresses the air on the other side of
the tank's bladder. When enough water gets in the tank to pressurize the air to
the shutoff pressure of the pump (say 45 psi), the pump stops. Next time you
open a faucet, the compressed air in the tank pushes water out, and through
your piping to the faucet. The pump will not come on until enough water has
been pushed out of the accumulator to drop the pressure back to the pump's
startup pressure (30 psi).  Thus the accumulator reduces wear and tear on the
pump by reducing the number of times it must start and stop. Plus it provides an
air cushion in your piping system which reduces water hammer (pipe banging
and rattling), which normally reduces pump-caused noise.”

   Once again, while the oven was removed to FOM, I installed an expansion
tank in the water system to do just what Netboy suggested. Unfortunately the
only space to be found for the tank is behind the oven. On the upside, remove 6
screws and disconnect the gas line and the oven is out. I purchased our
expansion tank from H.D. The smallest one they had. As with Netboy, I had to
“jury” rig a flexible faucet line to the PE tubing tee. Be sure to check in the
photo album for more pictures.
January 2007
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