Green "hue" related to filter issues?

[cpjolicoeur]

Long time member (since 2009) but very infrequent poster/visitor due to the fact that the methods here just work and I haven't needed a lot of help.

This year however, I cannot seem to get rid of the "green hue" in my pool no matter what I try and I continually will get a fine build-up of "green matter" on the bottom of my pool that no amount of daily brushing and vacuuming will keep from coming back.

I've done several SLAMs and I pass OLCT with no issues which means, to my understanding, I don't really have any organic growth going on inside the pool.

This is leading me to wonder/think that perhaps my sand filter is just retaining some of this organic matter and not filtering it out completely and just sending it back through my return. Is this typical. For a bit of history, I purchased a new sand filter 4 years ago and have never replaced the sand as my pool guy told me you dont need to and it's actually better to leave it in there packed tight.

I do normal backwashing when required and have only once done a vacuum to waste, just this month in an effort to try to clean up my current issue. I'm starting to wonder if I need to do some kind of deeper cleaning on my filter which lead me to this thread on deep cleaning a sand filter.

I have never done something like this, or even opened my filter. Is this possibly my issue and something I should pursue?

Here are the stats if anyone is curious:

18ft above ground, round pool.
~ 7900 gallons

FC: 5-7 depending on the day
TA: 90
pH: 7.5
CYA: 50

 

[kimkats]

You will not believe how much junk and stuff comes out of your filter when you take it apart and clean it!

I say do the deep clean and see what you find. Use a shop vac if you go all of the way of taking the sand out. I put the vac in my wheelbarrow so I can dump the sand in there instead of having to bend down. It is also an easy way to wash it.

If you do take your sand out be very careful putting it back in. Put a cup of such over the pipe so no sand goes down it. Fill the filter halfway up with water to help protect the laterals from damage.

Kim

 

[Richard320]

To see if something is bypassing the filter, rubber-band a sock to the return and see if it fills up with anything. And look around at windowsills and patio furniture and parked cars nearby. Are they covered with pollen or dust? Then so is your pool.

 

[cpjolicoeur]

I don't believe pollen is an issue this time of year where I am (Rhode Island). We had strong pollen early in the spring, but for the past month or so there hasn't been an issue with pollen collecting on surfaces. My pool is normally covered by a solar cover as well, so that would prevent a decent amount of pollen from entering the pool directly if that were the main issue. It is possible tho.

Assuming that matter isn't bypassing my filter, what are the possible issues here? My water is clear, and I survive overnight loss tests fine, I just have daily collection of "greenish" material on the bottom of my pool that causes my water to appear greenish and daily brushing and vacuuming don't seem to fix it completely.

This is the first year I've had this persistent issue, normally a few days of brushing and vacuuming and constant filtering make it go away. I'm not sure what I should try next as all my chemicals and water are balanced to appropriate levels and nothing seems to be actively growing based on the SLAM and OLCT numbers.

 

[Pauls234]

I think I had a similar problem last year, I'd vacuum junk off the floor and within a couple of days it would be there again. All of this while passing the OCLT, minimal chlorine consumption, and a solar cover on much more often than not. It was baffling to me, though I suspect it was somehow bypassing the filter. As I would vacuum the cloudiness of the water slowly increased, and it even appeared as though the cloud was coming from my return at one point, though it was hard to tell. That all suggests filter being bypassed so I started to wonder if dead algae was simply too small to be fully captured by my super clean cartridge filter?

Well, I changed out my liner this year so that junk is all gone and things are clear as ever.

I would first try Richard's idea of seeing what you catch in a sock on the return side to confirm that this is a filter bypass issue.

The other possibility is very low level algae problem that is hiding behind a light, return, on a ladder or something like that, but usually an OCLT reveals that.

 

[cpjolicoeur]

Just to follow up, I did a deep cleaning of my sand filter last night after work and then brushed and ran the filter all night. Things do seem to be noticeably better this AM. It looks to me a few more brushing and vacuums and things will be cleared up in a day or so.

I'm going to also put some DE into my sand filter for the first time ever as well to try to give a little extra boost to it's filtering ability.

 

[kimkats]

Just make sure to babysit the filter when you add the DE.

Kim