DE from return ports at every pump startup

[PoolFunYikes]

I’ve seen a couple threads on this but still puzzled. I have a DE filter (Pentair FNS plus 36) for my inground pool. I’ve noticed all 3 return jets show a cloudy burst of DE starting at about 20 seconds after starting the pump. It subsides within about 30 more seconds. I’m assuming the initial lag is the time for water to travel from the filter to the jets. I had this issue about for a few months and thought it was because of worn grids. I disassembled and inspected and saw no signs of cracks in the manifold, o-ring in good shape. I rinsed each grid and could not see any visible tears. I decided to replace all grids with new ones in case the material was somehow wearing out. It’s now 3 weeks after install of the new grids and I am still seeing this startup burst of DE which is clouding water on each start. I am sure it is DE because when it settles I can feel it’s abrasive texture.

If I shut the pump off and restart it does the same thing again.

No air bubbles are coming out of the jets on startup, so I don’t think it’s a suction leak. I tried running pump 10 seconds to Waste this morning before starting the Pump to see if it was due to anything getting back into the suction lines, but when I switched back to Filter I had the same burst of DE from the return jets.

I paid extra care on making sure the manifold was well seated on grids when I reassembled it and that grids were between their correct alignment channels.

The only thing I can think of next is that the manifold has some issue not visible to the naked eye. Wanted to know if there is anything else that I might be overlooking. thanks!

 

[Texas Splash]

Yikes, I'm curious, how old is your filter? You've been waiting on this one for a few days with no reply, so I'm going to tag @Richard320 to see if he has an idea as to what may be causing the blow-by after start up.

 

[Richard320]

All I can think of is the air bleed tube and screen.

 

[HermanTX]

It is most definitely a leak in either the filter screens or the manifold. What is interesting is that it is only a small burst of DE each time you turn on the pump. If it was a hole in the filter screen, it would stream through for a longer time. Since you replaced the filter screens, suggest you look closely at the manifold. DE must pass through either one of those items to enter back in the return water to the jets.
You may want to check the operation of your 3 way valve as well just to ensure that is seated properly. Move it from filter to another position, run the pump, turn off the pump, then turn it back to filter position. If you had moved it to backwash position earlier for that process something may have gotten wedged and needs to be cleared.

 

[PoolFunYikes]

Yikes, I'm curious, how old is your filter? You've been waiting on this one for a few days with no reply, so I'm going to tag @Richard320 to see if he has an idea as to what may be causing the blow-by after start up.

Hi I believe my filter is going on 20 yrs old, I believe it’s the original for the house

 

[PoolFunYikes]

It is most definitely a leak in either the filter screens or the manifold. What is interesting is that it is only a small burst of DE each time you turn on the pump. If it was a hole in the filter screen, it would stream through for a longer time. Since you replaced the filter screens, suggest you look closely at the manifold. DE must pass through either one of those items to enter back in the return water to the jets.
You may want to check the operation of your 3 way valve as well just to ensure that is seated properly. Move it from filter to another position, run the pump, turn off the pump, then turn it back to filter position. If you had moved it to backwash position earlier for that process something may have gotten wedged and needs to be cleared.

The bleeder tube and screen are intact. One thing I noticed was that the bleeder tube screen does have some play to it, ie not a tight compression fit, but not sure if it is supposed to have that. I replaced the MP valve spider gasket a few months ago and sealed it to the valve base with RTV. That was something I just rechecked two weeks ago, and it is still firmly in place and looks to have a healthy seal surface.

I did not backwash since installing the grids a couple weeks ago... just set to filter and added my 6.5 scoops of DE for a new grid of 36 sq-ft. I also made sure the filter base had no cake of DE when I had the whole thing apart to install the grids. Thanks for your help!!!

 

[Hien Nguyen]

After backwashing about two weeks ago, I filled up my Pentair FNS Plus 36 DE filter about the same amount as you using the DE scoops, and I had the same issue as you for a few days. It turned out that each scoop of DE is about one pound of DE, using 7 scoops means 7 pounds of DE. Redoing the backwash and only using 3.5 scoops (about 3.6 pounds per Pentair instruction), the issue went away and my pool is now crystal clear. I hope this help with your situation.

 

[PoolFunYikes]

After backwashing about two weeks ago, I filled up my Pentair FNS Plus 36 DE filter about the same amount as you using the DE scoops, and I had the same issue as you for a few days. It turned out that each scoop of DE is about one pound of DE, using 7 scoops means 7 pounds of DE. Redoing the backwash and only using 3.5 scoops (about 3.6 pounds per Pentair instruction), the issue went away and my pool is now crystal clear. I hope this help with your situation.

Thank you!!!!! Thank you!!!!! I was mislead by the DE bag which says a 32oz coffee can sized scoop is equal to 1/2 lb of DE. After reading your reply, I just went and weighed a scoop and you are spot on... each holds 1lb!!! See photo of 15oz mostly filled scoop.