Keeping FC stable with chlorine tablets

[xszaszax]

Hi,

A fairly new hot tub owner here. I'd like to ask a question related to chlorine tablets, which I use to sanitise the spa. My problem is that my 20g chlorine tablets dissolve too quickly (2, max 3 days) and as a result, my FC levels are raising high. I use a plastic dispenser which has a few holes on it and the dispenser is in the skimmer.
The SPA is ~1150liters. It has an always on filter motor, which is currently set to 2x8h cyclea each day.
When not in use, the temp is set to 25C, when in use its 37.5C. 
The SPA cools around 3-4C overnight when not heated, so it rarely sits on 25C.

Unfortunately i only have access to "simpler" water measurement tools, so I can only measure PH and FC right now.
PH is kept between 7.2-7.6

The water is 1 week old, and it's on the harder side of the scale.

Yesterdey we used the tub, after which FC dropped to around 0.1PPM. Added a fresh tablet right after, which reduced to roughly half size after 16 hours, and the FC leves raised to around 4-5PPM.

How could I reduce this effect?

Thanks in advance.






 

[RDspaguy]

7 hours ago, xszaszax said:

dispenser is in the skimmer.

Nooooooo!!!!!

I've been fixing spas for 26 years. If you want to know me well and see me often, dissolve acidic chlorine tablets in your skimmer. 

I recommend the dichlor/bleach method as described in the sticky thread at the beginning of the chemistry page.

[waterbear]

Trichor tablets dissolve too fast in the hot waters of a spa. They are also very acidic and can cause damage. Use a different source of chlorine or switch to bromine.