Answers

If you are installing a Hot Tub you will need a Concrete base or a solid base of Pavers or Stone, it must be level to distribute weight evenly. This ensures no water damadge to the bottom of the unit as well if there is any type of warranty on your unit the base insures you are covered for certain damages. I always suggest to my clients they should read the manual and installation instructions to see why they are installed the way they are. Below I have attached some alternitive options for a base other than concrete. I hope this helps!! wood and Flagstone option below. the 220V is important because you want to know your electrical will no fail without enough support, you will need a dedicated breaker with the 220V which any Electrician with your company or the clients will be able to do this. it will make it through think and thin. 

I work with a lot of pool guys and also have a pool   On an anual contract you should expect to pay 2500-3500 to open, close and maintain your pool for the year. 

There are so many variables that will affect the overall costs of maintenance, chemicals, etc.  For starters, where you live makes a difference in how many months of the year that the pool will be operational and energy costs will vary from region to region.  

Another factor to consider is if you will rely on a pool services company to open and close your pool annually or if you will be doing some of these services on your own.  The cost to open and close a pool is determined by the size of the pool.  In addition, many companies (including ours) offer discounts on pool chemicals if purchased in February, March, or April.  This can save customers a lot of money.  

In general, figure your annual costs could range from $500 to $4,000 depending on what services, i.e., openings/closings, weekly maintenance, repair, chemicals, etc. that will be used compared to how much you plan on doing yourself.

Your pool builder should be able to give you a fairly accurate assessment when you get to the final design stage.

I know i am late but for future people reading through this should also consider automatic pool covers if you are looking for all year round safety.  The safety covers mentioned above are more for winterization or covering your pool during a time you dont want to use it.  They take time to install and are not an in season friendly option.  

automatic safety covers like coverpools are a key switch operated safety cover that covers and uncovers the pool in a matter of seconds.  When installed by a professionaly trained installed they can easily hold the weight of multiple adults and children.

I'm not familiar with cartridges but you can buy an aromatherapy canister (hot tub warehouse online has them) in which you put aromatherapy beads whichare available many places (such as spa depot). You can add aromatherapy beads and liquid directly into the spa as well.

Loop Loc is a great product for safety fencing around pool areas. 

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