Sand Filter + Fine Debris = No Good?

[habajaba]

Ok, I have to admit, I'm new to the sand game. Our old house had DE. Even still, I haven't been doing pool maintenance for 6 or 7 years now. So I'm a bit rusty.

Our pool was extremely dirty this spring. It had been left open all winter, filter never ran after initial fill in early September. The PB came and dumped a lot of chlorine, fired up the pump, cleaned out all the big debris with a leaf bag and over a week or two kept vacuuming until clean. I then took over the job.

Every few days, I've had to vacuum out dirt as we still have a lot of unfinished area around the pool. This has been fine until the last 4 times. I'll get it all clean, it looks great. The next morning, about the same amount of junk is back in the pool, settled in the corners and vinyl seams. This is way more than the "normal" amount that was getting in before. So, I'm almost positive that it's just going right thru the filter. PB says that's life with a sand filter, even though HE was the one who convinced me a sand filter with zeobrite was just as good as DE. So I tried adding enough DE to raise my pressure 1psi and vacuumed again. Same result. I also put a knee high around my vacuum plate to make sure it caught anything big I vacuumed. That caught a ball of junk about an inch around. But I still have the fine stuff returning to the pool. I swam down and put my finger on it and it scatters like crazy as soon as my finger gets close. PB says my only option is to vacuum to waste as sand will never filter out this small stuff. Is this really true?

For those who are curious, this is how the pool looked this May after they shocked it back to clear water -

 

[JasonLion]

The sand/zeo filter should be able to handle that, though it might take a while. Sand filters can sometimes let things through if there isn't enough sand in the filter or if the sand gets channelized of if the pump is drastically oversized or if the main valve is broken (letting water past without going through the filter). If you put a skimmer sock/kneehigh over the return you can tell if it is really going through the valve/filter or not.

Very fine dust can stay suspended in the water for several days. Each day, for up to a week, more of it will accumulate on the bottom as it slowly comes out of suspension. I get something similar to what you describe for several days after each major storm. Within a week everything is back to normal. Running the pump 24/7 helps with this, but there is always water that doesn't go through the filter so always new silt while it lasts.

 

[habajaba]

You know, we did have a storm around the time this started. Maybe I'll give it a week to see what happens. The strange thing is the kneehighs in my skimmers aren't getting brown, so it seems like none of the silt is coming in thru the skimmers. And thank you, silt was the word I was looking for!

As for the filter/plumbing. The filter has been backwashed a few times recently due to all the original debris. So I doubt it's channeled. The only problem I can think is the sand is pretty clean now. But I figured the DE would "fix" that. I've been running the thing 24/7 since it came on. I figured until I get settled in, that's the best way to make sure everything is balanced and working right.

Just because I'm dense, how would one go about attaching a sock to a return?

Last but not least, I added the borax and acid last week before this all started. My bright idea was to put it all in thru a skimmer. The thought process was that way the acid shouldn't settle on the liner and cause any problems. But now, I'm wondering if dumping that valume of acid right into the filter caused a problem? It was about 5 gallons of acid, 2.5 one day and 2.5 a couple of days later if I remember right.

 

[JasonLion]

You can usually get a sock to stay on with rubberbands, it depends on your return pressure and the shape of your fitting.

Adding acid to the skimmer can in theory damage the pump seals and heater (if you have one). To the extent that this happens it is normally a very slow process. Even several gallons of acid, if poured slowly with the pump running, are very unlikely to have had any detectable effect.

 

[duraleigh]

Acid is the one item I prefer not to put in thru the skimmer. I put it in the return flow thereby distributing and diluting it quickly into the pool. That said, it's done now and it didn't stay in there but a few seconds and it was somewhat diluted by the time it got to the pump. Moot point. I wouldn't dwell on it.....bet your pump is fine.