The OTO chlorine test does not bleach out, so if that's what you have in your old simple kit, that will verify whether your chlorine level is 0 or through the roof. I think the FAS-DPD test is good to at least 50PPM FC, so your levels would have to be pretty high indeed to not get a good reading.
Do you have any idea if you have any metals, such as iron or copper, in your pool? Did the pool store ever test for that? Ever use copper-based algaecides, for example?
It is also important to get a good estimate of your CYA level, as there's a big difference in shock level between 25 and 90 CYA, so that is important for shocking the pool.
Do you have any idea if you have any metals, such as iron or copper, in your pool? Did the pool store ever test for that? Ever use copper-based algaecides, for example?
It is also important to get a good estimate of your CYA level, as there's a big difference in shock level between 25 and 90 CYA, so that is important for shocking the pool.