I'am finding little pices of plastic in the bottom of my hot tub it is a dreammaker 500

This may be a little late as you may have already found the answer. But most "Fantasy" spas have "Balboa" control system. They are either a heat control knob, or Up/Down arrows on the spa side control system.
If you have the know & it is all the way turned to max position, and still not hot enough, then you may well have a faulty "Temperature Sensor". Get a replacement from your local DreamMaker dealership. Easy to replace.

Dreammaker spas are usually a lower voltage spa(120 instead of 240V) make sure you got a motor of the same voltage, and even if its the same voltage, make sure the Amperage does not excceed the maximum allowed amperage on the hot tub.

Thats the problem with Dreammaker tubs, access can be a pain and theres no easy way of getting to the pipes.

I would usually gain acces from the underside which ensures that any holes that need to be made to gain access wont be visible in the future.

Good luck locating the leak.

Kind Regards,
Ian.
http://hottub.synthasite.com