Low pressure reverse Osmosis


Old 01-27-13, 11:06 PM
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Low pressure reverse Osmosis

I have a Watts 5 stage water filteration under my kitchen sink. The water pressure is very low and the tank does not fill. The unit is only six months old and I have already changed all the filters once due to the same problem 2 months ago. The tank pressure is 6 psi. The tank does not have a pressure valve, just an input for the water and a pressure nozzle. Can anyone tell me what is going on?

Old 01-28-13, 12:42 AM
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Are you on city water or well water?
If on well water what is the pressure tank setting?
Has the pressure always been low?
Old 01-28-13, 04:47 AM
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I would assume that if you already changed the filters once that when you did so it operated for a time but has quit again.....Is this correct?

There will be a fitting to measure bladder pressure, usually with a cap screwed onto it.
Your water has to be within certain parameters to get a reasonable service life; over 40 psi while the unit is operating and under 10 grains/gallon hardness are two important ones.
Do you get any waste water when there is no output?
Are you sure it is connected correctly?

You can check the output by turning off the water supply then disconnecting the line to the pneumatic tank, put the hose from the bladder tank into a pail and turn on the water and see if you have any flow.
If there is reasonable flow then the bladder pressure could be too high.
Old 01-28-13, 12:47 PM
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No the pressure was fine in the beginning. I am getting my water from Hetchhetchi dam in san francisco. The water pressure is perfect. The only thing I can think of is that the first filter (5 micron sediment cartridge) is dirty again (after 2 months). The tank never gets filled more than a third of it's capacity which is the part I don't understand, since the water from the city is normal and the tank pressure is within range of 5-7 psi. Yes I mam sure it is connected correctly since it worked fine when it was first installed. I have ordered some more sediment filters and hope that will solve the issue.
Any more ideas?

Thanks guys
Old 01-28-13, 12:55 PM
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A bladder tank never fills completely. The usable capacity is typically 1/3 or so of the nominal size of the tank.

The precharge pressure for RO systems is typically 8 psi and to properly set the precharge pressure the tank must be emptied completely and then the pressure is checked using the schrader fitting on one end of the tank.

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