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Posted:  4/24/2008 5:40 PM #20240
Ann Marie
Member
Total Posts:1
Last Post:4/24/2008
Member Since:4/24/2008
Subject: di VS tri-chlor
I have a fiberglass pool, which chlorine? Di-chlor or Tri-chlor is best for the fiberglass surface/

Ann Marie


Posted:  4/24/2008 7:00 PM #20241
chem geek
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Total Posts:921
Last Post:6/10/2015
Member Since:12/12/2006
It doesn't matter which source of chlorine you use in terms of your fiberglass surface: Trichlor, Dichlor, Cal-Hypo, Sodium Hypochlorite (chlorinating liquid or unscented bleach), Lithium Hypochlorite. With any concentrated source of chlorine you want to add it slowly over a return flow so it gets thoroughly mixed and for extra safety can use a brush to make sure none settles to the bottom. Trichlor comes in tablets/pucks or sticks and dissolves slowly and is very acidic, so is normally used in a floating feeder or an in-line chlorinator. The others are typically added directly to the pool.

The differences between the different types of chlorine are mostly in what additional substances they add to the pool. The basic rules are as follows:

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

Since CYA and CH do not go away, they can build up over time if you use the above sources of chlorine and do not have significant dilution of your water. Higher CYA levels make chlorine less effective so that you need to proportionately increase the FC level if you want to keep away algae. For manually dosed pool, making sure the FC level never gets below 7.5% of the CYA level will prevent algae growth (up to a phosphate level of around 3000 ppb which is very high). A usual FC target is 10% of the CYA level.

If you decide to use Trichlor or Dichlor (Trichlor will have CYA increase more slowly for the same FC), then an alternative would be to use a supplemental algaecide, either PolyQuat 60 or a phosphate remover. That will let you not worry about the increasing CYA level as much. It's more expensive to use Trichlor, however, if you account for the pH Up product you need to maintain pH and for the algaecide. Trichlor's main benefit is its convenience since it dissolves slowly so you only need to add more tablets every 5 days or so.

If you use chlorinating liquid or unscented bleach (6% Clorox Regular or off-brand Ultra), then you may need to add it every day unless you use a pool cover that keeps out the UV rays of the sun in which case you might need to add the chlorine twice a week. If you want to automate chlorine addition, you can use The Liquidator which you can read more about in this thread.

In any event, you should seriously consider getting a good test kit, the Taylor K-2006 (not the K-2005) you can get at poolcenter.com here.

Richard




Posted:  4/24/2008 8:17 PM #20242
waste
Member
Total Posts:75
Last Post:6/12/2008
Member Since:1/9/2006
THANK YOU RICHARD!!! - That post explains things very well and simply enough for us, ''non chem geeks'', to understand!

I hope all pool owners will read this and ''take it to heart!''

Having worked for 4 pool companies in 4 states starting in 1988 - what I know about pools could fill a couple books... what I don't know could fill a couple libraries ;)


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