I have leak at main jet where flex pvc joins coupler what size is inner diam can i cut tube out and put reducer in or some other fix

Buy a reducer to solvent weld to the PVC. Then use a band clamp to connect the flex tube.

Get a rubber splice joiner for that size of PVC Pipe. Just cut the pipe with a hacksaw and maybe another inch for clearance to put the joiner over both pieces of pipe and apply clamps. If you forget to put the clamps on then just unscrew them completely and wrap around the sleeve and tighten. Got mine at a plumbing supply, Lowes should have them.

You can run 2" all the way if you want. I f you have 1 1/2" coming from the filter you will have to bush it down at some point.
If it comes from the filter in a larger size it will be best to run that size to the heater but 2" probably wont hurt.

If the break is in the flexible tubing that connects the nozzles it is most likely spa-flex. This is the same size as nominal schedule 40 pvc and can be repaired with standard pvc fittings, primer and glue. Make sure the surfaces are clean and dry before repairing them and also allow at least 24 hours cure time on the glue.

It is very easy to cut the hole. It is also very easy to lose control of the drill and brutally gouge the tub. You need a strong drill and the correct size hole saw. Measure it carefully. You will only get 1 shot at this. Don't try to go too small thinking you can just make it bigger. That will not work as well as you think.
The hole saw needs to be a full circle of teeth with a center drill bit that sticks out further than the ring. You use a marker to put a dot on the tub where you want the drain to be centered. Then, you place the drill bit on the dot and slowly drill your pilot hole. When the ring of teeth make contact with the tub, they may want to skip and bounce. This will combine with your downward force to gouge big ugly chunks out of your tub.
I have scrapped many a tub by this exact procedure. You must control any and all bounce by firmly flexing your arms. You cannot allow any sudden upward or downward movements with the hole saw. You can give yourself a little more control by making the center drill bit as long as you can, but still firmly secured.
If all goes well, you will have the right size hole in the correct location. Sand or grind down the underside of your drain hole just a little. This will give your drain a flat surface to hug when you screw it together. A lumpy bottom may cause a leak. A thin bottom may crack during installation.
Take your time and you should do well. Good luck

it is not....you will have to cut it...that means you will have to get some hose to add in and a coupler to connect the 2 cut ends back together. There is a glue made by Oatey...called rain-n-shine, that will glue the hose to the pvc.

you can use a scissor cutter or a utility knife and make a nice square cut in the hose. After replacing the nut, hopefully you can find one, you can get a pvc coupling, the hose is the same size as pvc pipe, and use pvc glue to reattach the 2 ends back together. Use Oatey Rain-N-Shine glue....it is in a light blue can and the actual color of the glue is blue.

Yes It Should but might drag a little more when towed

most of those systems are plumbed with PVC, but some do use flex throughout the home...
If yours is PVC, visit your nutone dealer and get a new outlet/elbow.
Trim the old elbow off with a drywall saw or other small saw (if you have a sawsall, that is fine) and glue the new one in
if it is flex tubing, it's easier; the elbow threads on. just be sure to hold the tubing so it doesn't drop down,

try this:
you might but it will depend if it is pvc then yes any other material you might be able to use a waterproof epoxy but it will harder to repair because of the epoxy but the pvc you can prime and glue the seam from the inside..