What is the ideal total alkalinity level for a spa, as presented in the provided context?

The ideal total alkalinity level for a spa is generally recognized to be around 100 parts per million (ppm). This level of alkalinity helps maintain water chemistry balance, which is crucial for effective sanitation and to prevent corrosion of equipment and surfaces.

While some options suggest higher or lower values, maintaining total alkalinity at the recommended level ensures that pH levels can be stabilized more easily. A total alkalinity level around 100 ppm acts as a buffer to keep the pH levels from fluctuating due to the addition of various chemicals or due to the presence of contaminants in the water. Hence, the selection of an alkalinity level of 100 is standard practice in the management of spa water chemistry.