Problems with inline Rainbow erosion feeders?

[Hilton]

I have several Rainbow 320CN in-line erosion feeders installed at various pools. Two give me problems, I'm hoping someone can give me some insight.

The first is on an outdoor spa. The water line and valve is installed on the lower port. The feeder fills at least part way with air on a daily basis, but still seems to work. This doesn't seem to be a problem. But when turned "off", it still feeds chlorine into the spa at a high rate. Seems to me it must be leeching it through the bottom? I don't have this problem anywhere else, as far as I can tell...what could be causing it, and how can I prevent it?

The second is more troublesome. It is for a small outdoor pool (50,000 L). The water line and valve were installed on the lower port; when this problem began I moved the line and valve to the top port. The problem is that the feeder fills with air very quickly - sometimes in as little as 8 hours. Once a certain amount of air gets in, it stops working. If I drop 4 pucks into the skimmers (illegal, btw), the pool's chlorine level will stay at the right level for about 3 days. If I drop 4 pucks into the feeder, I will have 0 chlorine the next day, and most of the pucks remaining.

Both have new O-rings on the lid and fresh teflon on all connections.

If I can't find the problem, perhaps a workaround solution - could I get away with installing an automatic air bleeder (like this one) on the feeder? I fear it will come down to that, or replacing with a non-inline feeder... Actually on that note, I wonder if I can just plug the bottom of the feeder and install an outflow line at the top port? Turn the inline into a regular feeder...just stuck to the pipe.

 

[JohnT]

Air in the feeder is normally in reality a lack of water. Could be lack of flow from the system or it could be scaling or some other crud in the inlet line.

The unit feeding chlorine when off sounds like maybe the check valve isn't working.

 

[Hilton]

Unfortunately, there is no lack of water. The water level is always well into the skimmer, no possible source for sucking air down the lines. Also, little to no air in the pump.

I recently plumbed in an "out" line onto the feeder, with a check valve; this has actually improved its performance quite a bit... it actually feeds chlorine into the pool now, and doesn't get as much air in it for some reason. It's surprising, since I actually haven't plugged the bottom of the inline feeder yet - the plug I had didn't fit, haven't had time to pick one up that fits. So right now, it is operating with an "in" line that takes off directly below the feeder and goes to the top port of the feeder, and two out points - an "out" line that comes from the bottom port and reconnects about a two feet downstream (one foot to the left, elbow, one foot down), and the original port through the bottom.

 

[JohnT]

Unfortunately, there is no lack of water. The water level is always well into the skimmer, no possible source for sucking air down the lines. Also, little to no air in the pump.

What I mean is that the normal off mode of the feeder is to be full of air, and then water flowing in the pipe causes it to fill with water. Water isn't being picked up and forced into the feeder, probably because the outlet is clogged.

There is a small screen and check valve in the bottom of the feeder that can get gummed up and cause the feeder to quit.