Water not fully filtered on DE4800--what to check next?

[Ryan723]

Hi all,

Thank you for the great resource here...learned a lot reading already.

The Problem:
I just opened my pool and cannot get my water to clear. I pulled a bucket of return water and it is still cloudy AFTER being filtered. In the past my return water is sparkling/crystal clear. Normally the pressure rises quickly when clearing the just-opened water. Pressure is VERY slow to rise (~2psi--7 to 9) after a couple days of running. Usually I see a 50-100% increase in 24-48 hours of the early-season clearing. I know my system...it can go from pea-soup to seeing the bottom of the shallow end in <6 hours. And total clearing in a couple days. We're at 4 days and I still can't make out the bottom in the shallow end.

The system:
- ~20k gallon in-ground vinyl liner
- superpump (older but i rebuilt all seals, etc 2 years ago)
- variflow multiport (new spider gasket last year)
- hayward DE4800 48 sq ft DE filter (~20 years old); grids have only 3 seasons of use.

What I have done:
Took the filter apart and cleaned the grids. Once at startup and then again to check for tears/holes/cracks etc. All were fine both times.

Replace the Z5 oring on the inlet elbow in the DE4800 (top of the filter manifold to the return line I the filter. It looked a little worn and I was grasping at straws. No help.

I took apart the multiport. The spider gasket is fine and it shifts modes very smoothly.

Backwashed and recharged filter several times between disassembly of the filter. It is running at 7.5PSI recharged on very clean grids. This is slightly (maybe 2psi) lower than I remember the charged clean-grid pressure usually.

Water is somehow bypassing the filter elements...but I cannot find where?!?

Anyone have any suggestions of what to check next? I'm out of ideas!

Thanks all!

Ryan

 

[jblizzle]

Welcome to TFP!

I see no mention of following the shock process described in Pool School. If you do not kill the algae first, then the filter will struggle to clear the pool.

So you inspected the grids for damage and made sure everything was seated properly?

Have you checked the condition of your backwash valve gasket?

 

[Ryan723]

Jason,

Thank you for the response and the welcome.

Yes, I shocked (more than) adequately and have the pH on target. Any hint of algae green is gone...the water is blue/white cloudy.

I disassembled the Variflow multiport valve and checked the spider gasket and valve assembly. All looked very good--I replaced the spider gasket last year. I am fairly confident that it is functioning correctly. It doesn't leak out the waste port during operation and changes mode very smoothly.

I have cleaned, inspected, and reseated the grids twice now. I cannot find any tears or holes in the grids and the manifold has no cracks. And the grids are reseated in the manifold snugly and tightened down well.

This one really has me puzzled. I feel the problem has to be inside the filters since the multiport is OK.

Thank you!

Ryan

 

[jblizzle]

How do you define "shocked"?

Was it this: pool-school/shocking_your_pool ?

Post up a full set of test results.

 

[Ryan723]

Jason,

Thanks for following up.

I only have a cheaper test kit, but I roughly followed the method outlined in the page linked.

Having read more here, I will be looking for a full test kit soon.

Prior to shocking, I had pH on the high end of the range at 7.8.

I had used two pounds of Ca(ClO)2 at startup and then I used trichlor-s shock about 2 hours later. My test kit only goes to 5.0 FC, and it was well off scale after the shock addition.

This lowered the pH, which is now 7.4.

FC is about 5.0 now at two days after shocking.

I don't have a CYA test, but suspect it to be in the moderate range because we had quite a lot of rain dilution at the end of last season (rainy plus Hurricane Sandy).

TA is high at about 350 on my test kit. I will try to take the water in for a test before I buy a more complete test kit.

Could the high TA cause the unfilterable cloudiness?

Thanks again!

 

[jblizzle]

Well, no way to know if you have actually killed all the algae without performing the OCLT, which requires the FAS-DPD chlorine test.

Also, without knowing the CYA level, you have no idea what FC level is required. (that Trichlor shock was adding more CYA). What do you historically use to add chlorine to your pool?

No, the TA would not be causing cloudiness ... But sometimes the use of cal-hypo can. Although in this case, algae is more likely.

Read the rest of Pool School (button at upper right of the page) if you have not already.

 

[Ryan723]

I've made my way through most of the Pool School documents--that's a great resource.

The initial cloudiness was definitely from algae growing before we opened the pool this spring. It was very green on the bottom and in the water.

Understood that I can't know that all algae is dead without better testing. And that I can't determine shock level without knowing CYA. Historically, I have typically used stabilized Trichlor tablets for daily chlorination and cal-hypo for shocking. There is a chance that the CYA is quite high.

After reading here, I will be transitioning to BBB...wish I had found this site sooner!

I pulled a 5-gallon bucket of water from the return and it looks nearly as cloudy as the water in the pool (when viewed in the same bucket). That is what is leading me to believe I have something physically wrong with the filter system.

 

[jblizzle]

With a DE filter and as much stuff in the water as you are describing, the filter should be clogging pretty quickly. Also, your filter is smaller than we would recommend, so it likely will require frequent cleaning. On the plus side, at least your pump is not oversized as seems pretty common.

{BTW, We would recommend at least 56 sqft DE filter ... I have the 60 sqft on my pool}

What is your filter pressure? What is the clean pressure (right after a fresh DE fill)?

We recommend backwashing when the pressure goes up 20-25% of the clean pressure ... this could be within hours for a DE filter which is a hassle, but not as much as a cartridge filter. Sand filters certainly are the easiest when trying to clear a swamp, but take longer to filter everything out.

 

[Ryan723]

Current pressure is about 8.5 after a full night and most of today running it (33PM local time here).

I just recleaned the grids and recharged last night. Pressure was about 7PSI.

I should have writtent it down, but I seem to remember last years clean pressure was about 9-10. I would heave decent flow until about 15 PSI and drastically reduced output by 18.

I am used to back washing the first day I open the pool as the filter usually clogs right up after a few hours, but usually with good clearing of the water.

I am seeing almost no pressure increase relative to what I am used to seeing given the current pool cloudiness.

That's what's making me think water is bypassing the grids somehow....but I can't find where.

Thank you for the recommendations. I would certainly go larger when I replace equipment. I've been happy with the DE filter and don't mind the extra work of more frequent backwashes. This system is old, but (financially) I would like to get a little more life out of it.

I disassembled the finger again this morning and can confirm no cracks in the out "outlet elbow assembly" plus I put a fresh oring in it yesterday.

Thank you!