The older style LP tanks do use an internal left handed thread. The new tanks all have the "OPD" (overfill protection device) and they also have an external right handed "worm" type thread. You have two options: get an adapter at Walmart for about $10.00 or, check the date on the old LP tank you have, if it is twelve years or older, then when you have it refilled they will require you to have it re-certified. It is probably cheaper for you in the long run just to do a tank exchange for about $16-$18 bucks. That way you are good for another twelve years. As far as your question about running the bbq on NG, it won't work without a conversion. LP gas is at a much greater pressure than NG so, consequently the orifices are smaller for LP than NG. You can check with Aussie and see if they offer an NG conversion kit. If not, you can attempt to drill out the orifices by hand. There are some places on this discussion board as well as others on the net that talk about how to do this. If you do that, you can also get a 12' Natural Gas hose with a quick disconnect on the end that would fit (maybe without an adapter) on your existing stub from your house and the bbq. I just picked one up from Home Depot. It was made by Char Broil in the accessory area. In either case good luck and happy grilling. bsbbq

Thanks for the quick response. After posting my initial message, I called my local gas company and explained what I had done. They told me that I needed to remove the regulator on the grill. They cited the reason as the regulator that is currently on the large Prop. tank will regulate the flow of gas to the grill. They mentioned that if I left the regulator on the grill, that the flow of gas would be less than needed to operate the grill correctly. Does this sound like it is correct to you? Thanks again. -Scopas

I converted my Bluestar Rangetop myself. Prizer-Painter sent me the parts. It took about an hour to make the changes then adjust the shutters and low flame. Now that I know what I'm doing it would be a 15 minute job.

Looking at the Thermador Planning Guide, there is neither an LP nor a NG conversion kit for any of the Pro Grand ranges. Pro Harmony Dual Fuel have an LP conversion kit, but the all-gas ones do not (nor is there a natural gas conversion kit.) You will need to contact Thermador support to find out what nozzles and regulator will be needed. It's more than 6 easily-accessible nozzles, too, because you have to convert the oven burners as well in your all-gas range. Plus the griddle or grill, depending on what that additional location is. Once you start getting into the regulator and manifold on a gas appliance, you would be wise to have a gas-certified technician do the work.