Cloudy Pool Very Slow to Clear (If iat all!)

Causes and cures for cloudy swimming pool water.
Milky pool water, white, pink, brown, purple, black cloudy water.

Cloudy Pool Very Slow to Clear (If iat all!)

Postby Guest » Wed 18 May, 2011 04:48

Problem: Cloudy water incredibly slow to clear after pool opening.

TC: 7ppm
pH: 7.5
TA: 170
CYA: 50 (this was done with dip sticks so may not be accurate, the above reading were done with tabs)

My pool: In ground concrete
Pool chemicals: Dichlor
My pump & filter: Sand Filter
Other info:

This is my second year owning a (11,000 gallon) inground pool with a sand filter.

1 month ago:
After taking the cover off (and discovering a green pool!) I dumped in two large drums of liquid chlorine to shock. Left with the pump on 24/7 for 48 hours before adding in a bottle of liquid algae killer. This was 2 weeks ago. I expected the pool to clear up after a few days (like last year) but it hasn't. It remained a milky blue colour. Actually i went away for 4 days so didn't backwash too much and the chlorine had burnt off while i was gone.

When i got back i checked the pH which was a little high (7.8) so i lowered that to 7.6ish and reshocked this time with granule chlorine (Dichlor). Again i threw in half a bottle of algecide i found left over by the previous owners. All this time I backwashed the sand filter maybe once every 2-3 days.

2 weeks ago:
Next i had a crack on my filter lid which meant i had to turn the pump off for a couple of days until fixed. Since the repair (2 weeks ago) i have been maintaining the Chlorine levels between 4-10ppm using granules Dichlor. The pH seems to be constantly creeping up so I have been adding pH minus granules at the rate of about 250g every 2-3 days.

The pool has been clearing ever so slowly but is taking a long time (it only took about 2 days last year). I have not backwashed the filter for 1 week and that seems to have co-incided with a bit more of an improvement in the clarity.

Also - any suggestions of a reasonably priced test kit available in the UK that will help me accurately test CYA, CH etc?

Any suggestions what is wrong and why it is taking so long?

chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2381
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Cloudy Pool Very Slow to Clear (If iat all!)

Postby chem geek » Wed 18 May, 2011 21:27

Palintest SP 315C.

Do not use Dichlor. Remember the following chemical facts that are independent of concentration of product or of pool size:

For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm.

If you've been using Dichlor regularly, your CYA may be much higher than 50 ppm. Read the Pool School for more info including the shock level of chlorine needed once you find out your true CYA level. You may need to do a partial drain/refill to lower your CYA level.

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