Liquid Chlorine Strength in PoolMath - Differences between Effects of Adding and Home

[mgtfp]

There is an inconsistency in the interpretation of the entered bleach strength between the FC-tab in PoolMath's Home overview and the Effects of Adding, that sometimes creates confusion, especially for members outside of the US.

In the Home section, everything makes sense. Bleach-percentages above 9% are interpreted as Trade-% (g Cl₂/L [%]), Bleach-percentages of 9% and smaller are interpreted as NaOCl weight-% (g NaOCl/g [%]).

This reflects the custom that liquid chlorine with 10% and 12.5% strength is usually sold specifically for pools, and the Trade-% is easier to use to calculate PPMs.

Liquid chlorine with strengths below 10% is usually sold as household bleach, and it seems to be labeled as NaOCl weight-% in the US.

Percentages of 9% and smaller, PoolMath internally transforms into Trade-% to calculate the resulting PPM-change in a given pool volume:




But in the Effects of Adding, PoolMath only "knows" the bleach-strengths that are typically used in the US: 5.25% (NaOCl weight-%) for which 5.4% (Trade-%) is used, 6% (NaOCl weight-%) for which 6.17% (Trade-%) is used, 8.25% (NaOCl weight-%) for which 8.49% (Trade-%) is used, 10% (Trade-%), and 12.5% (Trade-%).

Any entered percentages that are different to above values get "rounded" to one of these values. The following graph shows which Trade-% PoolMath uses depending on the entered bleach-percentage:



For example, any percentage larger than 12.5%, PoolMath will interpret es 12.5% (Trade-%).

I remember a member using 15% bleach who got confused about the differences between Effects of Adding and the Home-section.

In Australia, household bleach gets sold as 4.0 Trade-% (Trade-% and NaOCl weight-% are actually pretty much identical here, but Australia makes things more complicated by labelling it additionally as NaOCl volume-% (42 g NaOCl / L)). But when entering 4% into PoolMath's Effects of Adding, Poolmath "rounds" that to 5.25% bleach (NaOCl weight-%) and uses a Trade-Percentage of 5.4% for the PPM-calculation - resulting in wrong PPM values for an addition-calculation. In the Home-Section, the calculation results are correct when entering 4%.

Is it possible to implement the same bleach-strength interpretation in Effects of Adding that is used in the Home-section?

 

[ajw22]

@Leebo another for the list.

 

[Newdude]

As far as the over 12.5% is concerned, it was determined that due to how fast chlorine degrades at stronger concentrations, almost nobody would ever see 12.5% by the time it got to their home. Most 12.5% jugs would be 10 by the time they were used.


Below 6% on the other hand, is a very valid concern.

 

[JoyfulNoise]

It’s certainly possible but it would be up to our app developer to make the changes to the app. Not impossible but it would have to go through the standard development beta cycle to ensure that nothing breaks in the production app version. Updating Apps with Apple is a time consuming task that often results in a lot of rejections or feet-dragging on the part of Apple. So a change like this would need to be bundled with other updates to make it worthwhile. We don’t have a team of app developers to work on this (just one dude who does it for “fun” and out of the kindness of his heart), so don’t be surprised if this request takes some time.