Rainbow feeders air problem

[Hilton]

I have a large number of Rainbow 300-29x offline and 320cn inline feeders in use at various pools. Some of these pools are very old and have minor unlocatable air suction leaks, causing small amounts of air to travel through the line. Some of this air ends up in the chlorine feeders, in some cases dry-locking them (no water flow). In one case this happens on a daily basis; others it is slow or random.
Has anybody ever added something to these to remove air? Irrigation systems have a simple check device which allows air to escape the line, but seals shut when water hits it (via a floating ball). Would this work, installed in the lid or in a new port slightly higher than the return line, or might it allow chlorine gas to escape too? I tried installing one in the line to the feeder, but it didn't catch any air.
Any other ways I can solve this?

 

[JohnT]

I think the problem isn't air, but lack of water being pushed into them. They work by being full of air and then allowing enough water in to wet the pucks according to the valve setting. They get clogged with puck residue and quit working. I used to have a good explanation of how they worked, but I'm not sure where it is. I'll see if I can dig it up.

 

[Hilton]

I make sure they're full of water before closing them. They do work at whatever setting (usually between 0.5 and 2), but eventually fill with air and stop working.

The only ideas I have, since the air source can't be found, is an air relief valve on the feeder, or an air trap on the inlet line (basically put another large vertical tube halfway on the inlet line with the water in and out at the bottom). The second one assumes air is coming in through the inlet, and not sneaking past the check valve on the bottom of the inline feeders...

 

[JohnT]

There is most likely no air source. You aren't getting enough water flow to fill the chamber. The chlorination drains when flow drops. Low flow from the pump, a clogged check valve or screen are probable causes.

The 300 can't easily form an air pocket because it has a top outlet.

 

[Hilton]

In each of the cases where I have air in the feeder, there is also air in the pump. These are mostly 320 inline feeders, but also affects a 300-29x. Installations with no air visible in the pump have zero problems.

 

[flyingvranch]

There is a hose extender kit available that you can install. Or you can just do this quick fix which consists of taking out the top plug and the bottom feed valve assembly and exchanging them . ( Install the feed valve into the top hole where the plug was and installing the plug into the bottom hose where the valve was.) Be sure to use teflon tape and hand tighten only. Now your feed hose (black) is too short. The easy solution is to take the old hose to Home Depot and buy about a foot of irrigation tubing the same size. Install this and your problems will be pretty much cured. It's only a five minute job really. I have done this to the thirty five pools that I clean and have yet to have the air lock problems that used to drive me crazy with old pools just as you described. Hope this tip helps!

 

[flyingvranch]

Here is a pic of one that I modified as described. The feed valve is now in the top hole and the plug is in the bottom hole. A longer piece of tubing is installed also.

 

[JoshU]

It certainly sounds like it could be a bad check valve at the bottom of the unit also. You may want to check it out.

 

[xjarcher]

I realize this thread has been quiet for quite a while. But---- I have a question.
I just ordered a Rainbow 320 and I plan to do the mod in this thread from the start. I'm in MI so freezing etc is a factor and I will need to disconnect the feeder and bring it inside. To this point I use flex hose as it's the most practical. I will do PVC with some screw connectors if it's the best way to get water into it. The question is what size? Is 2" a necessity or can I use 1 1/2"? Can I still use flex line on the output side?
Thanks all.