Multi-vessel spas

A spa system comprising:

• a first vessel configured to hold water;
• a second vessel configured to substantially hold the first vessel, the second vessel further being configured to hold pressurized water;
• a circulation system comprising at least one water jet, wherein the water jet is positioned between the first and second vessels and is configured to use water pressure in the second vessel to send water into the first vessel;
• and
• a watertight seal around a connection of the water jet, wherein the first and second vessels are positioned to receive leaking water upon a malfunctioning of the watertight seal.

A method to prevent damage in a spa upon a failure of a watertight seal, the method comprising:

• attaching a water pump to the spa;
• attaching a first vessel with a second vessel, wherein the first vessel is configured to hold water for the spa, and wherein the second vessel is configured to hold water in a pressurized cavity, wherein the water pump is configured to pressurize water in the cavity of the second vessel;
• connecting a water jet between the first and second vessels, wherein the connecting comprises attaching the watertight seal at a water jet connection;
• and
• using water pressure in the pressurized cavity to send water from the second vessel into the first vessel with the water jet, and wherein the watertight seal is configured such that water leaks between the first and second vessels if the watertight seal fails.

A system for a spa comprising:

• a first vessel configured to hold water and one or more persons;
• a second vessel attached to the first vessel, wherein the attachment comprises a twin-sheet bond between the first vessel with the second vessel;
• and
• embedded channels between the first and second vessels for air and water circulation in the spa.