Backwash

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rdshackleford

rdshackleford

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Jul 30, 2015
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Coatesville, PA
My water is crystal clear and when I backwash after a week (no pressure rise), the backwash water is very green, like pea soup color, for a minute. I only backwash because I know the gunk is sitting in the filter and I feel I should get it outta there. Is this wrong? Am I just wasting water?
 
Re: Backwash - how often?

Prior to my pool resurfacing late last summer I had to backwash once per week. The plaster was old and had been painted and the paint was coming off when I brushed or ran my dolphin. With new plaster I've only backwash once this summer since the pool cleared up after the slam I had to do after opening.


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Re: Backwash - how often?

Back washing is generally recommended when you have a 20-25% pressure rise. Sand filters actually work,better a little dirty as it helps catch smaller particles.

Now,what worries me is your green pea soup description. It sounds to me that you have a low level algae bloom going on. The filter is catching it (not all) and it is growing in the filter until you backwash.

You need to,conduct an OCLT to see if something is growing in the water you can't see yet.
 
I did have a visible algae bloom situation in the pool up until last week when I learned what my proper chem levels should be from TFP. :) I read a bunch, got the FAS-DPD kit, and things are improving rapidly.

I changed the filter sand last weekend and backwashed the new sand before running the filter. Today I did a backwash, got a minute or 2 of greenish/tanish backwash water, and the PSI lowered less than 1/2psi (from 13psi which on my very old gauge may not be numerically accurate.) It was not quite the pea soup darkness as the previous weekend, and the backwash took less time to clear. The brown dust-like substance collects on the bottom in a few days, mainly on the liner seams and in the corners. The Nautilus Plus robot gets everything spotless and its filters come out very green like a pond.

I did the OCLT test last night and lost only 0.2 FC between 8:30pm and 6:30am.

Water is crystal clear and my chems this morning are: FC 5.8, CC 0.2, pH 7.7, TA 90, CH 250, CYA 60

-R
p.s. thanks to the moderators for splitting my post into its own thread
 
While the dust on the bottom can be pollen settling, the fact that the filters are green and you had (or have) an algae bloom, if you didn't SLAM your pool, just getting your levels right won't eliminate it.

I believe you need to SLAM and get rid of the algae and then let numbers get back to normal. Then that should eliminate the green soup in the sand filter and your nautilus filters.
 
R, I would think of running your FC levels at SLAM level for the next couple of days just to see if your water can get any clearer.

Kim (shhhhh but also I do a short backwash after running my vacuum because I do not like the thought of the dirt just sitting in my filter)
 
I'm a little confused. Wouldn't running the OCLT show if there was algae in the water? And my water is crystal clear and the OCLT drop was only 0.2ppm.

The brown/tan dust seems to be happening less and less every day now. If you look close at the photos, you can see a little bit of this sediment collecting on the liner seams, about 24 hrs since the last cleaning (which is much less than what was accumulating last week).
P1050774.jpgP1050777.jpg
 

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Well with a .2 OCLT loss, crystal clear water and no CC it is safe to assume what you are seeing is blowing into the pool, not growing there.

A little late in the season for pollen, but I know my neighbors sunflowers have a yellow powder coming off them now. Anything around the yard that may be casting off a dust/powder?
 
Certainly its a big open area and whatever floats by can cause some sediment. I have not noticed pollen on the furniture for a long time now. It was a light brown or tan color, but when disturbed it would take on a more greenish hue as it dispersed into the water and disappeared. Too fine of a dust to be felt when I tried to touch it. Too bad I just sold my microscope on ebay, or I would try to capture a sample. I know a lot of chemists, maybe one of them knows a microbiologist that can take a look. But the dust seems to be lessening over time. Maybe it was remnants of an algae bloom on its way out? Before last weekend, my sand was very old and probably not enough of it. And since I changed to the stronger variable speed pump this year, maybe it was forming channels down to the laterals. When I took the S-240 clamshell top off, I found the sand on one side of the filter had a conical depression, sort of like a sinkhole.
P1050757.jpg

Back to my original question, is it better to wait for a pressure rise in the filter before backwashing, or backwash more often as long as the backwash water is greenish?

-R
 
I always wait for the pressure to rise, unless I'm adding a little cellulose fiber (DE replacement) to the sand. A slightly dirty sand filter gets smaller particles out of the water.
 
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