Hope everyone out there is staying busy ran across a questionable gas connection today.
can you decrease a 3/4 in gas line to 1/2 in then back to 3/4 in appears to me that it would causing a restriction possibly starving the water heater that it was connected to (that was not operable at time of inspection). The main is 3/4 in black pipe and water heater, furnace and stove are being supplied by 3/4in CSST.
Thank you for any advice in advance
No you cannot. Just recommend evaluation and repair by a licensed plumbing contractor.
As Martin said that would be a NO-GO, Patrick. 
Thanks guys for taking the time to give me some answers hope you all are staying busy.
The funniest part of the whole thing they had permits spread out on the countertop. This is about the fifth time in four weeks that I have found things that had passing permits (found three electrical panels that had no grounding at all)
I give all that credit to our Baltimore City inspectors
Have a good weekend thank you
How far was the run to the water heater after the 1/2" nipple? what type of water heater? tank or tankless? if it’s a tank based standard WH, it will be a none issue unless the run of CSST is long. 1/2" up to 10 feet can handle ˜100k BTU appliance. So even if they did not upsize (which is better, not worse) and kept it at 1/2, it would still be fine.
It’s best to have a licensed professional plumber size and evaluate the fuel distribution piping on site. Unlicensed opinions are just that. Sizing a fuel piping distribution piping system can be tricky.
There is nothing to evaluate (unless! there is a visual indication of an issue), it’s not rocket science! it’s always easy to defer and make your client waste $$$ The only concern is a 1/2inch nipple because the home inspector is not familiar with the basics of how a plumber sizes gas pipe. It’s not rocket science, look up the chart and be familiar with it. Don’t be that Joe home inspector that takes client’s money and delivers little. Know that a tankless wall gas water heater uses A LOT of gas and being fed by long length of 1/2" pipe will likely be an issue. A typical 40-50gallon tank based water heater is only 40-45k BTU appliance. A 1/2" nipple is NOT going to be an issue.
It was a standard tank water heater and was about 6 ft of 3/4 inch csst after the 1/2 inch nipple.
I would not call it out based on my knowledge and experience. I recommend you get yourself familiar with how sizing is done. If you feel concerned, especially since the unit was not operational, call it out and recommend review of the nipple at the same time when the unit is put in use. The unit should be commissioned by a licensed HVAC/plumber. This way the client does not waste money by just having someone “look at” the nipple.
It would be best to report as “evaluated and possibly repaired by a licensed plumbing contractor”. Reduction of a fuel piping system and increasing pipe size is not acceptable.
You can take the advice from a licensed gas fitter or a fly by night home inspector in an unlicensed state. It’s your company and liability.
Don’t be fooled by fly by night inspectors, gas piping sizing is very serious.
