Sand filter at 40psi. No return and skimmers seem to be leaking? HELP!!

[jspec]

We started up our pool this year with little issue and it has been working great. We like everywhere around the midwest have had almost 100 degree weather everyday with little rain. This caused a ton of alge and cloudiness in my water. So my wife was using a ton of clairifier. I started to notice that the sand filter was at 40psi more and more. So I changed the sand filter sand and assumed it would fix the issue. Well during the time I was going to get sand and time to change the filter I noticed tons of bubbles or air in the returns. I shutoff the skimmers and the bubbles disappeared.
Anyways I changed the sand and rehooked everything up. It was fine for a few days but all of a sudden I have 40 psi again and no flow. I am still just coming off the main drain as I have not had a chance to look more into the skimmers. I am not sure what or where to check about this 40psi no flow issue? Any suggestion?

Thanks in advance,
Jason

[Watermom]

Hi jspec and welcome to the Pool Forum!

100 degree weather and no rain do not cause algae. Low chlorine levels cause algae. Can you please post a compete set of current water testing results taken with a drops-based kit? Make sure that CYA is one of the readings you give us. Also tell us the type of pool and volume and exactly what all you have added to the pool, meaning ingredients and not product names.

Regarding pressure on your filter --- I assume you have been backwashing?

[jspec]

I only have the 7 pad test strips. I have been meaning to get a test kit. I assumed it was from the heat but it could be the no flow. I have a clorine feeder inline. The free chlorine has been ok everytime I have tested. Thw numbers I get right now are
Total hardness 250
total chlorine 2-3ppm it is a little darker than 2
free chlorine 1ppm
PH 6.2-6.8
total alkalinity 40 ppm
cyanuric acid 0

As far as what we have added just the 3" tabs in the chlorinator and some conditioner.

Oh My pool is a gunite inground pool. and about 38000 gallons. I have a 300 lbs sand filter 400k heater and automatic chlorinator. The pool has a main drain and 2 skimmers and 3 returns. It is a lazy L shape.

[Watermom]

If you have been using an automatic chlorinator, then you have some CYA. Probably LOTS of it. Test strips are pretty worthless. You really need a good kit. In the meantime, do you have a reputable pool store who can run a set of tests for you? Just don't let them talk you into buying a bunch of stuff. Post the numbers -- especially CYA. We can't really advise you well without knowing what that reading is. (See the Best Guess Chlorine Chart in my signature below.)

A critical problem (if your numbers are right) is your pH! Anything below 7.0 is acidic and will damage your pool. Please go to Walmart today and pick up a cheap OTO/Phenol Red kit (yellow and red drops) and test. Also pick up several boxes of 20 Mule Team Borax (laundry aisle). Post your pH reading ASAP. Once we confirm your low pH, we'll instruct you on how much Borax to add. Also get a few boxes of baking soda. (Your pool store would also have the OTO kit, but not the Borax or baking soda.)

Have you been backwashing your filter?

FYI -- When you think of something you want to add or see a typo you want to fix or whatever a short time after you post, you can just click on the EDIT button in the lower right instead of writing another separate post.

[jspec]

I actually just found a older test kit from Leslie. No cya but it should get me close. I figured out that if I bypass the sand filter it seems to work fine. Why would my sand filter keep clogging eve after I backlash? The sand is not even a week old at this point. I will run by Walmart later to get some borax and baking soda.

[Watermom]

I wish I could better advise about your filter, but that is just not my area. Hopefully somebody else will be along soon who can. Everybody must be busy today; nobody has been around the forum too much!