I own an old Culligan RO system with a particulate filter, carbon filter, RO filter and post carbon filter all connected by tubes in an open environment. Replaced filters and tank is only 3-4 years old but cannot seem to get any water flow into the tank, have checked lines for kinks and plugging, seem ok. Water is flowing into the system at the beginning but doesn't come thru. Water pressure while not great has been effective in past. Any suggestions Don

it may take a few minutes to purge air from system, open ro fausct and let it bleed air and run water with spurts.

https://www.youtube.com/watch?v=-guPFrVEbgM

Here is a manual for a Culligan H-30. Basically the same unit. The diagram shows how to replace o-rings.
http://www.freshwatersystems.com/support/H-30.pdf

RJ

Pre-filter and carbon block filter are changed annually. The membrane is only changed every 3-7 years depending on water quality coming in, TDS and usage. Fourth filter is an in-line carbon filter that goes on the line up to the RO faucet.
RJH2O

When you put air in the tank did you make sure all the water was out of tank? In a three gallon tank there should be 7 lbs of air, 10 gallon 10 lbs of air.
There can be many reasons for no water in tank.
1. Bad bladder in holding tank. No back pressure on membrane (all water going to drain)
2. Faulty membrane (all the water going to drain)
3. Bad capillary tube (all the water going to drain)
4. Plugged check valve at top of membrane (no water)
5. Faulty water feed valve (piercing valve)
6. Fines from post carbon filter have plugged up the manifold (head) of RO unit.
7. Bad valve on RO tank
8. Plugged drain line
RJ

The quick connect fittings need to be fully seated or when pressure is applied they will leak. If the feed is pressure is high to the RO I have seen this occur also. JG John Guest makes a small locking clip that goes on these fittings to hold them tight. Here is a link to JG which shows this application.
http://www.johnguest.com/Home/applications/beverages-and-drinks-dispense/Inch-Size-Accessories/LOCKING-CLIP.aspx
RJ

Too much pressure in holding tank will not cause leaks in the RO unit. All too much pressure in tank will do is cause low or no product water in RO tank. Older Culligan RO systems (H8, H83, H5) had fittings that used metal locking washers and these can cut the RO line after the RO has been moved around while changing filters. Newer styles (AC30, Water Tower) use quick connect fittings and the RO line may work loose after filter changes and system being moved around under sink.
Turn the incoming water off to RO, turn the water off on RO tank, open the RO faucet to relieve pressure and pull the line off feeding the RO tank, inspect (you may want to cut off a small portion of the line at the filter) check the o-ring and re-install.
RJ

I would pull out all the filters changed and check them. If a GAC filter is used as the post filter, before the RO tank, carbon fines can come out of the filter and can plug up the head on the RO system. Make sure the sediment pre-filter is not plugged and there is plenty of water supply. You may have lost pressure in the RO tank. A 3 gallon tank should have 7psi pressure when totally empty.
RJ

Turn off the incoming water supply, turn off the valve on storage tank, open the RO faucet and let pressure off. Have a pan ready, remove the sediment pre-filter housing and post-carbon housing.
Use latex gloves when changing filters, add 1 tsp bleach to each housing and clean them thoroughly before installing filters. Make sure all bleach is rinsed out before installing filters. Turn the water back on to system, turn the tank back on and run 2 tanks of water out before using water again.
RJ

For a 4-Stage system:
1. Open the housing caps of the components that house both the sediment and carbon filters (you may need a residential spanner wrench). Put each filter into its proper housing and tighten housing caps MANUALLY. Do not use wrench.
2. Repeat process with membrane housing and membrane (if membrane needs replacing).
3. Remove inline polishing filter by disconnecting tubing at both ends. Replace with new inline filter and reconnect tubing.

There may be several causes for this. Here is a list of things to look for.
1. If an activated carbon filter was installed many times carbon fines will plug up the head of the RO housing. Pull the filters out and flush the whole assembly with NO filters in it.
2. The capillary tube (which puts back pressure on the membrane to create water) may be worn out and all the water will run to the drain. Replace capillary tube
3. The automatic shutoff may not be opening to allow for water flow.
4. Shut the water off at RO tank and take the line off from RO filters to see if any water is flowing from housings.
5. The RO tank may also need air. If the air charge is low in tank (7 psi for 3 gal tank) no water can be forced from the tank.
6. If the RO is fed by a piercing valve make sure their is water coming from it.
7. Depending on what type of RO it is their may be a flow restrictor in head of membrane housing that can get plugged also.
I hope these tips may help you,
RJ