I have a customer who has a 22 Gal RO tank which feeds 3 lines out. The pressure at the Schrader valve is 35p.s.i. and the tank has water but no water is being delivered. No water comes out of Schrader valve when depressed. There is a P.S.I. guage to the left of the line feeding the tank (see photo) which read 35 P.S.I. but as soon as there was a demand for water that guage dropped to Zero. The Schrader valve still reads 35 P.S.I. . I do see that the discharge is at a constant trickle but I don't see an ASO or Check valve OR membrane in the system (they appear to be missing) to test. Very strange system, it appears to have a pre-scaler filter for raw water to a small pump to booster pump to 3 stage prefilter to (maybe an electronic check valve?) to Tank with 5th stage filter, but it has been running this way efficiently for 9 years! Any ideas?
RO tank pressurized but no water
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Bannerman
Well-Known Member
This is most commonly due to insufficient air pre-charge in the storage tank.
Tank pre-charge pressure is to be measured with a tire pressure gauge, after the RO system has been shut down and after the tank is completely drained of water.
Since the tank is waterlogged, with insufficient air to push the water out, either disconnect the tank, or open the lowest elevation RO faucet, then add small amounts of compressed air into the Schrader valve, until all of the water is eventually pushed out from the tank through the disconnected fitting or through the open RO faucet.
Once the tank contains no water, the pre-charge pressure is to be then set to 6-7 psi. The low pre-charge pressure will provide sufficient pressure to continue to push water to the RO faucets even while the tank contains a minimal quantity of RO water, and will also optimize the amount of production water the tank can store.
The ASO/ASV appears to be the device directly above the booster pump, where the pressure switch is located.
I anticipate the RO membrane will be either the center or right cartridge of the Culligan 3 quick change cartridge unit, and further anticipate, the check valve and drain flow regulator will be located under the top cover of the 3 cartridge unit.
RO tank air pre-charge, should be checked and adjusted on a regular basis, typically every 6-9 months while the sediment and carbon filters are being replaced. The membrane will typically require replacement every 3-5 years, once the level of TDS in the production water has risen to indicate the membrane is no longer as effective and is permitting some level of TDS to pass through.
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Michael Young
In the Trades
need better pictures. Rock the pressure tank. If it's heavy, you're waterlogged.
Try is bypassing all that filtration. If you bypass and have good flow, you have an occlusion somewhere in the filtration.
LLigetfa
DIYer, not in the trades
Depending on where the Schrader valve is, checking to see if water comes out may be inconclusive as there could still be a pocket of air above the water. The waterlogged bladder could be pressing against the bottom of the tank sealing off the outlet.
No water comes out of the Schrader valve, only air if I press it. Valve is on the top of the tank under the cap.
I found that water comes out of the Main Booster pump feeding the 3 pre-filter unit but no water comes out of pre-filter. I just replaced the filters. Tank is full but I'm not sure what you mean by water logged. Isn't the tank supposed to be mostly full?
Air precharge may be too much for the RO tank. With the water pressure zero, what does the air pressure measure? Seven to ten psi is typical.
If the pressure shows near zero, I would expect the bladder/diaphragm has failed.
If the pressure shows near zero, I would expect the bladder/diaphragm has failed.
I suspect your right because the pressure drops to zero after 1 glass of water. I think the only thing making it work at all is the water pressure itself coming into the line. Once it is used up it drops to zero again. That would be a defective bladder correct?
Bannerman
Well-Known Member
Try adding air before condemning the tank.
My plastic body RO tank slowly looses air on a continued basis, requiring air to be added every 6-months or so. This has occured since the system was first new and installed more that 15 years ago. No RO water leaks into the air chamber, and even submerging the tank into a tub of water, no air leaks are apparent, including from the Schrader valve, with or without the O-ring sealed valve cap in-place.
I suspect my plastic bodied tank maybe porous by nature, thereby permitting air to slowly migrate through the material, or perhaps the air migrates through the internal bladder.
Tanks designed for RO storage, typically will be equipped with a large bladder, to maximize storage capacity, while operating over a larger pressure range compared to a well system pressure tank.
Although the air pre-charge will be typically only 6-7 psi, when filled, the pressure can approach 60+ psi, particularly when a booster pump is utilized to increase the supply pressure to 80 - 100 psi. If a permeate pump is also utilized, that will permit a 90+% ASO to be utilized, permitting the storage pressure to rise to 90+% of incoming pressure before production is stopped. A standard ASO stops production at about 60% of incoming pressure.
As detailed above, add small amounts of air to push out the water currently constrained in the water chamber. Once all of the water is out, adjust the pre-charge, then if possible before restoring RO operation, check the pre-charge again after 2-3 hours, to ensure the pre-charge pressure remains consistant. If the tank won't hold air, or if pre-charge pressure has dropped in that time, that would be an indicator of a failed bladder.
My plastic body RO tank slowly looses air on a continued basis, requiring air to be added every 6-months or so. This has occured since the system was first new and installed more that 15 years ago. No RO water leaks into the air chamber, and even submerging the tank into a tub of water, no air leaks are apparent, including from the Schrader valve, with or without the O-ring sealed valve cap in-place.
I suspect my plastic bodied tank maybe porous by nature, thereby permitting air to slowly migrate through the material, or perhaps the air migrates through the internal bladder.
Tanks designed for RO storage, typically will be equipped with a large bladder, to maximize storage capacity, while operating over a larger pressure range compared to a well system pressure tank.
Although the air pre-charge will be typically only 6-7 psi, when filled, the pressure can approach 60+ psi, particularly when a booster pump is utilized to increase the supply pressure to 80 - 100 psi. If a permeate pump is also utilized, that will permit a 90+% ASO to be utilized, permitting the storage pressure to rise to 90+% of incoming pressure before production is stopped. A standard ASO stops production at about 60% of incoming pressure.
As detailed above, add small amounts of air to push out the water currently constrained in the water chamber. Once all of the water is out, adjust the pre-charge, then if possible before restoring RO operation, check the pre-charge again after 2-3 hours, to ensure the pre-charge pressure remains consistant. If the tank won't hold air, or if pre-charge pressure has dropped in that time, that would be an indicator of a failed bladder.
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After much research, I think I have it figured it out. The left top blue cylinder is a raw water scaler, into low pressure switch, to booster pump, into 3 stage pre-filter, out to high pressure switch, to tank, then to post (lower blue cylinder -polisher maybe?) filter to outlets. I opened the Culligan pre-filter and there is no membrane at all. There is an outlet for one but has a blank plug inserted into it. I believe they bypassed the membrane because of the high demand for water (services about 80 people) for K cup coffee machines and it was more cost / space efficient than adding more tanks just for coffee and 1 water cooler . With that said, the tank was water-logged and I emptied tank, reset the bladder pressure (9.5 lbs) and let it fill. I believe the high pressure switch is defective because it is waterlogged again and overfilling the tank. When I emptied tank again the pressure was right where I set it still, so bladder is OK.
Bannerman
Well-Known Member
I just reviewed the photos added after my initial reply.
That Flexcon H2PL33 tank is actually a well pressure tank which utilizes a diaphragm. As such, it is designed for a limited drawn down capacity, using a higher precharge pressure, compared to an equal sized tank designed for RO storage.
In zooming in on the device I initially thought may have been an ASV, I now see there are not 4 water connections but only 2, and since an electric cable appears to be connected, I suspect it may actually be a solenoid valve to stop water flow when the high pressure switch above, senses sufficient pressure within the storage tank/RO outlet.
That Flexcon H2PL33 tank is actually a well pressure tank which utilizes a diaphragm. As such, it is designed for a limited drawn down capacity, using a higher precharge pressure, compared to an equal sized tank designed for RO storage.
In zooming in on the device I initially thought may have been an ASV, I now see there are not 4 water connections but only 2, and since an electric cable appears to be connected, I suspect it may actually be a solenoid valve to stop water flow when the high pressure switch above, senses sufficient pressure within the storage tank/RO outlet.
Instead of installing a residential sized RO unit and attempting to make it perform better equipping it with a booster pump and well pressure tank, it would have been prudent to install a suitable capacity RO unit, equipped with an actual RO storage tank with sufficient capacity to satisfy their water consumption requirements.
There are 4 water lines, not 2. The wires you see are just the connections for the pressure switches hanging down so there is no solenoid valve there. The tank is a PL22 not 33. The tank does utilize a diaphragm though. I'm a bit confused as to why a solenoid would be needed. I thought the high pressure valve did that?!On another note, would you happen to know what the initial (empty) pressure setting should be for this 22 gal tank? I think this is still causing an issue. I know most RO systems are between 6-8 psi but being this is a well tank....
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