Decreasing flow rate

[CTX_Traveler]

I just opened my pool a few days ago and noticed that the water flow rate decreases significantly 2-3 hours after I started the pump. (Hayward S244T sand filter installed in 2012)
- Running a backflow and rinse will result in normal water flow for another 2-3 hours.
- Because the sand has been more than 5 years, I thought the media was the issue but after replacing with fresh sand the problem still exists.
- Additional thing that I noticed, I just need to put the filter on backflow/rinse for a few second and the problem will go away for another 2-3 hours.
- The pool water is clear and no debris

Any recommendation on what I should take a look at next? Do you think it is something to do with the spider gasket?

Thank you in advanced for the help!!

 

[Texas Splash]

Welcocme to TFP! Hard to believe, but your scenario sounds like a chemistry issue. Even though yoru water appears clear and good, excessive microorganisms will do exactly what you are describing. What we would ask at this point is to see a full set of water test results. Hopefully you have a TF-100 (link below) or Taylo rK-2006C test kit. See Test Kits Compared With results from one of those we can help. Please post results as follows:
FC
CC
CYA
PH
TA
CH

Thanks for using the forum.

 

[CTX_Traveler]

Thank you for the reply Texas Splash!! I never though or seen such issue if it is caused by excessive microorganism. Here a quick summary as requested. It is a 25K gallon saltwater pool.

- I opened it 3 days ago. Put 3 bags of shock, and chlorine tablets to bring the Chlorine level up before starting up the chlorine generator.
- results per test yesterday:
FC: 2
TC: 2
PH: 7.2
TA: 60 (just added 13 lb of baking soda this morning)
CYA: 30 (once the need to backwash is gone, will add the granule. Don't want to waste)
CH: 80 (will bring it up after TA is up)
Salt: 1200 (just add 200lb this morning)

Thank you again for the help!!

 

[Texas Splash]

Based on your low FC level, I would expect chemistry is the issue - algae. It's not always green or very obvious. One thing you could do is an overnight test -Overnight Chlorine Loss Test. If you fail the OCLT by losing more than 1 FC overnight, then a SLAM Process is definitely in order. So don't add anymore stabilizer until you know for sure (pass the OCLT) that there are no algae issues.

If you pass the OCLT, great. Increase the stabilizer and continue to balance items as required. FYI - Vinyl pools don't normally require CH unless you have a specific piece of equipment that mandates it. If you fail the OCLT, move-forward with a SLAM and your pressure issues should be resolved. Hope that helps.

 

[CTX_Traveler]

Thank you Texas Splash - followed your pointer and able to rectify the issue!!

- As for CH, I heard multiple feedbacks mentioning that lack of CH could cause your vinyl to wrinkle. Is that true? The only 2 pieces of equipment that has metal that I have in the pool is a ladder and the pump.

Thank you again for the help!!

 

[Texas Splash]

Glad things are working out. The low CH should have no bearing on your liner. A low pH however could if that was ever to happen over a significant amount of time. Have a great day.