Water Chemistry for an In-ground Spa

[panamax53]

A friend has a badly abused in ground diamond-brite spa. He uses it rarely as a splash pool and never heats it. I am thinking there is no reason why TFP levels should not be used for this mini-pool. I have read old posts in the forum where much lower levels of calcium are recommended. I cant make sense of that unless they failed to mention it was for a fiberglass spa?
Please dont suggest Bromine. The cost of a little extra bleach is all they'll ever want to deal with if they decide to start heating it occasionally.
Let me know if I am not on the right track to simply treat this as a swimming pool.
Thanks

 

[HermanTX]

The main purpose of Bromine for heated spas is that it holds up better at high temperatures for long periods of time. Clearly everyone with a spa/pool combo uses chlorine - even when spa is heated but it is for a short duration which is why it still sanitizes, however it is replaced by new chlorine when the spa is turned off and normal circulation with the pool. It is reasonable to treat it as a swimming pool but be aware of the advantages bromine provides over chlorine to be more stable at higher temperatures. You will also have to consider adding stabilizer as chlorine will dissipate quickly if exposed to direct sun. Suggest your friend read up on chlorine vs. bromine to ensure your friend understands the risks.