Generally, you do not need to drain your pool to convert it to a saltwater system. The main exception is if you have used an antibacterial agent containing polyhexamethylene biguanide to sanitize your pool, as these sanitation products do not mix well with saltwater systems. If this is the case, you will need to start fresh. You can either drain the pool or treat the existing water with a high dose of chlorine to remove the antibacterial agent. If you choose the chlorine treatment, wait several days to allow the chlorine to work before proceeding with the conversion. If you are unsure whether this applies to your pool, consult a pool technician.

The disadvantages of container pools come down to flexibility and customization. Shipping containers come in standard sizes, so the sizes and shapes are limited. They also have a very distinctive look, which may not suit the aesthetic of your backyard. 

Beyond that, while container pools are more affordable than in-ground pools, certain models can be more expensive. This includes the cost to heat your pool, since the metal walls have more heat transfer than other types of pools (which some brands circumvent with insulation).

The total time to install an inground pool typically ranges from 8 weeks to 4 months. This timeline can be influenced by several factors, including permitting, site preparation, and the construction process itself.

Key phases and their typical durations include:

• Permits: Obtaining necessary permits can take anywhere from two to six weeks.

• Excavation and Site Preparation: This phase takes about a week but can be extended by problematic soil, unexpected ground conditions, or the need to move underground utility lines.

• Construction: The actual build, including plumbing and electrical work, often takes one to two months. The pool material is a major factor here; a concrete pool needs about 30 days to cure, while installing a fiberglass or vinyl liner is much faster.

External factors can also cause significant delays:

• Contractor Availability: Spring and summer are busy seasons, and high demand can lead to long waitlists, potentially adding months to your start date. It is often recommended to start planning and getting estimates up to a year in advance.

• Other Delays: Weather, material shortages, complex designs, and other unforeseen challenges can extend the project timeline.

It's not ideal, and if your pool’s pH is seriously low (below 7), swimming can be dangerous until you raise it, potentially causing severe irritation and damage to the skin and eyes.

Keep in mind that low pH can also be responsible for damaging the pool itself. Acidic water can contribute to the cracking of your pool's liner, which may cost up to $2,500 to replace, making this an expensive fix.