Do I need to drain pool?

Causes and cures for cloudy swimming pool water.
Milky pool water, white, pink, brown, purple, black cloudy water.
Doug V
Pool Newbie
Pool Newbie
Posts: 1
Joined: Mon 19 May, 2008 11:02
Location: Michigan

Do I need to drain pool?

Postby Doug V » Mon 19 May, 2008 11:46

:( I am new to this site, and this is my first posting. I purchased a 15,000 gallon Viking fiberglass pool in 2004. It has always had chemical balance problems. I am located in Michigan.
When I opened the pool 05/01/08 I cartridge filtered the cloudy pool for several days and then tested the water. The TDS and salt levels came back extremely high even though this is not a salt water pool. Also the Alkalinity is very high, and I have been informed that I need to drain the pool. This is a real problem due to the fact the pool can pop out of the ground if drained, and the cost of the partial water replacement is over $500.
The readings are as follows:
Saturation index .7, TDS 3300, CYA 30, total chlorine 2.2,
free chlorine 0, Ph 7.9, tot. Alk 254, adj. total alk. 245,
total hardness 352.
I added 5 1lb bags of shock upon opening, but it appears the shock never dissolved as the shock was vacuumed out by my aquabot vacuum.
I am looking for an alternative to draining half of my pool, and also trying to determine where the TDS and salt is coming from. I chlorinate with 3" Trichlor pucks through a chlorinator. Please help!!!!

Update: 05/20/08 readings at 2 different testing centers:
Leslie pool tds at 3000+, salt at 1690, alkalinity 420, FC 8.0
Midwest pool tds at 3200, salt at 3130, alkalinity 157, TC 0.8, Fc 0.0

chem geek
Pool Industry Leader
Pool Industry Leader
Posts: 2382
Joined: Thu 21 Jun, 2007 21:27
Location: San Rafael, California

Postby chem geek » Wed 21 May, 2008 11:27

First of all, as you can tell from the varying readings from your pool stores, you cannot trust their pool water testing. You need to get your own good test kit: either the Taylor K-2006 kit you can get at a good online price here or the TF100 test kit from tftestkits(dot)com here with the latter kit having 36% more volume of reagents so is comparably priced "per test".

Since you have been using Trichlor tabs/pucks and I assume did so in years past and have a cartridge filter that does not get backwashed, your Cyanuric Acid (CYA) level is probably a lot higher than the 30 ppm that you quoted. With Trichlor, for every 10 ppm Free Chlorine (FC) that it adds, it also increases CYA by 6 ppm so it can build up rather quickly. High CYA levels require proportionately higher FC levels to prevent algae growth.

Because your pH and Total Alklinity (TA) are very high and it appears that your Calcium Hardness (CH) may be high (why the pool store measured Total Hardness is beyond me -- it is Calcium Hardness that is relevant), your pool is currently over-saturated with calcium carbonate. This can cause the water to become cloudy, especially if you've been adding Cal-Hypo for shocking the pool (and in the extreme it can lead to scaling).

As for the TDS, which is mostly salt, some of it comes from the combination of TA (sodium bicarbonate) and CH (calcium chloride) and some from CYA (cyanuric acid), but that would only account for about 700 ppm. The rest is probably just plain salt and comes from the chlorine since with ANY source of chlorine, for every 10 ppm FC this will become 6 ppm salt since chlorine becomes chloride which is salt. However, to get to the high numbers that you have would require quite a few years with lots of chlorine usage so does seem a bit strange -- normal pools are in the range of 500-1500 ppm TDS. At any rate, don't worry so much about the high TDS at this point -- I'm more concerned that the true CYA level may be high.

In the meantime, I suggest you do the following: 1) add acid to lower the pH. Since you want to eventually lower the TA as well, I suggest lowering the pH to 7.2 which will take 11 cups of Muriatic Acid (31.45% Hydrochloric Acid). This should help clear up cloudiness associated with the over-saturation of calcium carbonate. 2) add chlorinating liquid or unscented bleach (6% Clorox Regular or off-brand Ultra) to raise the FC to 15 ppm (as I presume your CYA is higher than 30, but don't know by how much) which is about 3 gallons of bleach. Buy lots since you'll need more to keep the FC high. 3) filter 24/7 and brush the pool to circulate the water.

After the pool clears up, you'll need to lower the TA level by following the procedure described in this post which has you lower the pH, aerate the water, and add acid to keep the pH low. To aerate the water more vigorously, you can buy a water fountain or something like this device.

If it turns out that your CYA level is very high, then you can dilute the water using continuous dilution so as not to lower your water level (that is, drain on one side from the bottom and fill from the other side). You can also use the sheet or silage bag method which will use less water -- you get a large sheet to cover the pool surface and drain the water from underneath while adding new water on top and let the sheet lower as the water replacement occurs (you need a very large sheet for this). The silage bag method is similar except you drain from outside the bags and fill the bags with water (which has them sink into the pool). When the bags are full, you dump their contents into the pool (i.e. turn them upside down and remove them).


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