Deep Heat Lines for spa?

[johnm92627]

Can someone tell me what the deep heat lines are for in a spa? My plumber is giving me the option. From what I understand it is a 3 way valve that diverts heated water from the heater. But how and why? This is for a gunite spa only with no pool.
THANKS!!!

[imfignewton]

The only thing I can think of is that water is being diverted to the bottom of the spa instead of the walls of the spa. Hope this helps

[johnm92627]

Does this help much for an oversized spa? Sounds like it would be minimal?