Returns losing Flow on Filter/ Not on recirculate.

[Jmpjack]

I have a Pentair whisperflo pump and an fns plus 48 d.e. filter setup. The problem is that my returns completely lose flow and the pressure in the housing gets up to 25-30psi.

There are 3 valves on the suction side:
-main drain
-skimmers
-pool/spa

Ive rebuilt and sealed all 3 valves. I've also replaced the pump skimmer o-ring and its well lubrcated fearing of a suction side leak.

I also replaced my d.e. grids and added fresh de of course (4 designated scoops).

I don't know what else to do. The system runs flawlessly on recirculate. However on filter, it will gradually build up pressure in the d.e. housing and restrict the return flow. If I backwash for a couple minutes it will remedy the problem temporily. However I have to do this 4-5 times a day to keep it running properly.

Once the pressure builds up to 25-30psi I turn be pump off and open the bleed valve at the top of the tank and a bunch of air comes out and after a few minutes I'll hear a bunch of bubbling and then the water recedes out of the pump skimmer. When I do this, then turn the pump back on it does make the pressure drop. Only when I backwash does it drop the pressure back down to operating level.

I'm not sure if this is related but I've removed the filter housing lid a few times and every time I do the breather tube screen on the bleeder tube is caved in and clogged with debris.

Please help, I've been fighting with this non-stop for several weeks. We had a pool service for several years that we let go after they kept refusing to deal with this issue and I need to figure this out.

Thank you.

 

[cowboycasey]

Welcome to TFP ☺

You have found the best thing about DE filters, they work great and that is the worst thing about DE filters they work great....

How does your water look, it is doing its job and filtering all the stuff out of your water

Please post your numbers so we can see what is going on ☺

 

[VikingPoolMan]

I have a Pentair whisperflo pump and an fns plus 48 d.e. filter setup. The problem is that my returns completely lose flow and the pressure in the housing gets up to 25-30psi.

I also replaced my d.e. grids and added fresh de of course (4 designated scoops).

My first thought would be that your grids are bad.... how long ago did you replace them? Did you use the filter to 'cleanup' your pool when it was in a nasty condition? How often do you backwash? How is your water clarity?

 

[Jmpjack]

Welcome to TFP ☺

You have found the best thing about DE filters, they work great and that is the worst thing about DE filters they work great....

How does your water look, it is doing its job and filtering all the stuff out of your water

Please post your numbers so we can see what is going on ☺

The pool is clear my numbers as of this morning are:
FC - 3/6
pH - 6.8
TA - 40
TH - 400
CYA - 30-50

- - - Updated - - -

My first thought would be that your grids are bad.... how long ago did you replace them? Did you use the filter to 'cleanup' your pool when it was in a nasty condition? How often do you backwash? How is your water clarity?

The grid's are less than 2 weeks old. I tried the acid wash on previous set and it didn't help which lead me to purchase new ones. They are directly from Pentair also.

I'm having to backwash a few times a day to keep the pump running properly and the pressure down.

On side note, my multiport valve sounds like it has an air leak. I know it's on the pressure side but couldn't the water going through it pull in air as it passes by? A venturi effect to a sort?

 

[VikingPoolMan]

You should not have to backwash several times a day - especially if you have new grids (and I assume you put the correct amount of D.E. powder each time). It sounds like there is something in the water (algae/oils/dead phosphates/etc) that is clogging up your filter.

 

[Jmpjack]

You should not have to backwash several times a day - especially if you have new grids (and I assume you put the correct amount of D.E. powder each time). It sounds like there is something in the water (algae/oils/dead phosphates/etc) that is clogging up your filter.

I'm all ears, this problem has kicked my butt up and down. How could I test for such a thing?

 

[VikingPoolMan]

I'm all ears, this problem has kicked my butt up and down. How could I test for such a thing?

A new 48sqft D.E. filter (new grids) with proper amount of D.E. on a 'clean/clear' pool should be good to go for many weeks. The pressure should not be rising in a few hours unless there is something in the water... If someone else has a different answer, please speak up.

Just so we are on the same page, when you say you have "clear water," I assume you mean the water is crystal clear so you can see what type of screws that are on the main drain cover? Is there anything on the bottom of your pool (powder/slime/etc)... and if so, do you have a suction side cleaner that might be sucking that into your filter? Do you have a painted pool and paint is possibly clogging up the filter? Do you use powder chemicals and/or add chemicals to your skimmer?

There has to be something in your pool water that is creating a "slimy layer" on the D.E. grids (and that's causing the pressure to rise quickly). If you can't physically see anything in your pool water, I'm not sure how to test for these things... apart from draining/diluting your pool, I don't know what else to tell you. Maybe someone else has some other ideas?

 

[mas985]

I agree. Sounds like an algae bloom. Run an OCLT to confirm.

 

[Jmpjack]

As far as the clarity goes, yes it it's crystal, no haze at all. However there is brown patches on the sides of the pool that I assume is algae.

I will do the OCLT test after the holiday. That would make sense after reading about that test bc my pool eats through chlorine like a snack. I have a floater with 3 tabs and 3 tabs in each (two) skimmers and they are all gone in a week. Which to my understanding is very fast.

Something I also forgot to mention, the pool runs smoother for longer periods of time when its undisturbed. But within 30 minutes of my kids swimming it backs up. I assume that could be bc the algae is getting stirred up and sucked in?

 

[mas985]

Yes, that is a good assumption because most of the dead algae will drop to the floor and then get stirred up by the kids.

I see a SLAM in your future.

 

[Jmpjack]

So I'm going to SLAM. However, what should I do about my current filter restriction so it works properly throughout the process?

Should I pull my grids and soak them in bleach for awhile and then add fresh D.E. prior to starting the process?

Also, is laundry grade bleach ok to use or do I need something something stronger?

 

[cowboycasey]

laundry 8.5% bleach is fine, sometimes the 10% from walmart ends up cheaper if they have it.. You may also have a HASA dealer near you, they sell 12.5% that is almost the same price but you use less so it lasts longer

The filter, you are really just stuck with backwashing a lot to start out as it is a great filter and is catching everything in life...

 

[mas985]

Does your filter have a recirculate mode? Run that during the SLAM until you pass OCLT. Then just vacuum to waste. Prevents having to keep cleaning your filter.

 

[Jmpjack]

So first of all I want to thank everyone for your help.
Believe it or not, I as able to fix the filter flow problem by adding D.E. I assume it was so low that it wasn't able to filter very well. I added 4 scoops and the pool has been working flawlessly for the past 5 days, with swimmers and all. The water is also the clearest I've ever seen it.
With that being said, I definitely still think I've got an algae growth due to the brown discoloration on the pool floor. Still plan to slam it just in case.