have powdery substance settled on bottom and ledges/stairs

I have a powdery dust substance that settles on the steps and bottom. when I vacuum it stirs it up in clouds and also comes out through the jets. also when I backwash I can see it coming out of drain. I have a sand filter. I use chlorine granules, chlorine tablets in a release tube, soda ash, and pool perfect and aglaecide. all this once a week after I vacuum. my readings are normal and ok except ta is a little high. I just started using the chlorine tablets because my pool pro said I was supposed to be using those all along because they allow the chlorine to work.... does anyone know what this powdery substance is and what am I doing wrong. pool is cloudy. SOS new pool owner

Welcome to the forum. We'll need some water testing results to be able to help. Use a drops based kit - not test strips. We'll need FC, CC, TC, PH, alk, CYA and calcium hardness. Also, tell us specifically (ingredients) what all you have put in your pool and the type and volume of your pool. Then, somebody here can take a look and offer some help.

my readings are hardness:250, TC:3, FC:between 2-3, PH:7.6, alk:120, Stabilizer:100. chlorine tablets that I put in a tube and it releases from there. My regime: once a week I test water usually all readings are ok. then I vacuum. after that I backwash then rinse. then I add chemicals. chlorine granules 3lbs, pool perfect-2 capfuls, algaecide-6oz, soda ash 2 to 3 lbs. pool is a fiberglass. my readings on test and drop kits are usually ok. I am a new pool owner bought a house with a pool. pool when we first moved in in november was beautiful crystal clear water. just leaves on the bottom. buy chemicals from the guy who maintained it for years. this is the recipe he always used and water was beautiful. the water remained beautiful until I started adding chlorine granules then got cloudy. I was not adding the tablets to the tube because i did'nt understand you had to use those with the chlorine. pool pro said put those in and should clear. did not clear and now I have this powdery substance. pool pro is super busy and hard to get on the phone. I have backwashed and vacuum to waste and can see the powdery substance draining out. pool still cloudy but will keep vacumming every day. not sure what this is or how to avoid getting it. any help would be appreciated

umm forgot to tell the volume. 27,000 gallons

"this is the recipe he always used and water was beautiful."

It appears the recipe is now causing you problems.
Sounds like your pool guy is having you add lots and lots of stuff that you don't need. Other than that, the biggest problem that I see is that you are not maintaining adequate chlorine levels for a pool with such a high cya reading. We usually recommend cya of 30-50. Yours is twice that high. We often suggest doing a partial drain, but with such a large volume, that would be a huge water exchange. You may decide instead of doing that, to just live with the high cya but you'll have to run higher than normal chlorine levels as a result. See the link below.

http://www.poolforum.com/pf2/showthread.php?t=365

I would suggest that you stop adding all the stuff that you are adding. Using those tablets - which I assume are trichlor, are what is causing your cya reading to get so high. Instead, just use plain, unscented bleach. That is what most of us on this forum use for our chlorine. Also, the chlorinating granules - probably cal-hypo - may be contributing to your cloudy water. With a cya reading of 100, you need to shock your pool up to 20ppm with bleach. In a pool this size, each half gallon (2 quarts) of 6% bleach will raise your cl by about 1ppm. For the next few days, try and keep your cl up to shock level without letting it yo-yo up and down and run your pump 24/7 while trying to clear the pool. After it begins to clear, you'll need to maintain cl readings between 8-15 all the time with your cya level. (Of course, if you decide to do a partial drain, those numbers will need to be adjusted.) I recommend that you buy the kit that is sold at the sister site to this forum www.poolsolutions.com as it will allow you to test high chlorine levels. Most other kits that you can buy will only test up to 5.

Stop adding all the other stuff. You don't need it, and it is probably contributing to your problem. Your ph and alk are fine for now. Hope this helps. Keep us posted of your progress.

ok thanks for the advice. now just to be clear. stop using the granules and take out the chlorine pucks. just add bleach to the skimmer until I get a reading of 20. keep it there until pool clears. then keep it at 8ppm. all this as long as my stabilizer reading is high at 100. is this correct. any idea what that powdery dust substance is.