Fleck 2510 - Air in pipes after regeneration

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Jeff DIYer

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Good evening. I have read countless posts on this site in researching my issue and haven't come across my exact issue or solution. Figured I'd give this forum a shot. There are a lot of knowledgeable folks on here. Thankful for any recommendations.

Background: Well, pump, acid neutralizer (5900-BT), AIO iron filter (Fleck 2510), and water softener (Fleck 5600 SXT). All working together for the three years since I installed the iron filter without issue. One night I wake up to LOUD air in pipes at 3am. Have had 5-10 seconds of air in faucets and toilet in upstairs bathroom following every regeneration cycle (every 3 days) for the past 6 months. I had my septic drained and I topped off my acid neutralizer with calcite to the 2/3 level a few weeks before this issue began. The septic drainage did make me wonder about venting issues causing some of the nighttime noises when the filter flushed. Ultimately, my only remaining issue is air in the faucet and toilet lines.

Steps Taken to Date:
- Well technician determined not issue at well or pump in utility closet. No leaks found. Said it had to be the iron filter.
- Ensured my other filters weren't regenerating at the same time by staggering schedules
- Bypassed the iron filter for 2 weeks and never had an air issue but water did start to smell without iron filtration
- Based on AFW's (seller) guidance, replaced piston, seals, and spacers - i did find a string of fiberglass in spacers but no other indications of issue
- Mailed to AFW who inspected, tested, and returned based on seeing no issue
- Programmed to various settings per Fleck hotline with no improvement
- Based on Fleck hotline, replaced check valve and air draw check valve
- Cleaned injector nozzle and screen
- Verified no visual damage to riser tube
- Verified control head is properly seated with o-ring to riser tube

Fleck hotline questioned pump keeping up with regeneration cycle.
- I calculated 6 gal/min based on filling a bucket directly from the well pump
- I watched a full BW and AD cycle. Pump pressure seemed to fluctuate between 40-55 PSI. I never witnessed air being flushed through the clear drain line so I assume the pump is keeping up with the filter. I did watch with a flashlight as the water level slowly lowered to the media level within the filter tank but never ran short of water before the AD cycle completed and returned to service. There was air in the lines after this test.
- I have seen air pocket in filter tank ranging from .5 inch to 1 ft from the top -i'm not sure what is normal
- When I bypass the acid neutralizer, there is no air in the plumbing during iron filter regeneration
- When I leave the acid neutralizer in service and set air draw to 0 on iron filter, I get no air

So, only time that air does not exist following a regeneration cycle:
1. Iron filter is bypassed entirely
2. Iron filter air draw is set to 0
3. Acid neutralizer is bypassed

Fleck hotline believes there are no remaining explanations besides media. My media is Ag Plus with a gravel bed. It is 3 years old. I am hesitant to invest more in chasing this if it is ultimately the control head. I'm also hesitant to spend $1K+ on a new control head to replace my 3 year old unit. I think I have exhausted most obvious troubleshooting and fleck hotline assistance. I did have a professional plumber come out but he was not an expert in filtration systems and could not help.

Hopefully these details spark some theories. Thank you in advance.
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