If you go with any sort of solar system, make sure it has a gas backup and not electric. My energy costs went up $100/month when I added our solar system down here in San Diego. I am now getting it corrected with the installation of a small gas tankless unit, using the solar storage system as a pre-heater. If you're building the home then many of the traditional drawbacks of tankless don't apply to you. You can build in the correct gas line and venting from the start. If I were in your shoes I'd probably go tankless (30 percent tax credit this year -- see the stimulus law or visit www.energystar.gov). If a single unit won't handle your demand then get two. And plumb it with the small tank system (10 gallon) for recirculation and to overcome any sandwich problems. This approach has been detailed in this forum somewhere.

It is likely air in the line leading from main to heater. I suggest haveing the propane company send someone back out because their service call is much cheaper than a plumber's. Relighting it yourself based on instructions gleaned on the net is not a good idea. . Time for a story about tinkering with propane gas. Man jumped out of a plane for his first parachute jump. Unfortunatly he wasn't paying attention when given instructions earlier about operating his chute. Just as he was giving up hope,he sees another man flying up toward him from the ground. As they passed he shouts "hey do you know how to open a parachute? "No,comes the reply,do you know how to light the pilot on a propane water heater?"

I haven't tried running the unit any more but I did do some double checking on the gas lines and think I have found a problem that would affect the sytem when it is heavily loaded. My gas meter is a "pound meter" running 1.2-2.2 psi. The gas meter feeds an Earthquake shutoff valve with a 1" inlet and outlet, which then feeds the low pressure regulator with a spring set at 6-8" WC. The problem I see is the outlet of that regulator is only 1". The 1" section is only 2 inches long after which it transitions to 1-1/4" pipe... but if I look at the gas tables a 1" pipe can only flow 286 CFH (~ 286K Btu/hr) at 50 ft and 259 CFH at 60 ft, the approximate distance to the furthest appliance. With all appliances running full tilt my load is about 485,000 Btu/hr. Thus, I do not believe the 1" section is large enough. The installation does not have a gas line drip leg before the Noritz unit. If that was an oversight by the gas piping contractor, the inspector also missed it, or we don't have the requirement in our local area. I'll be talking to the contractor about the 1" pipe section and lack of a drip leg this week. One thing I wonder about is the Noritz startup gas load... when it fires up the exhaust blower runs at high speed, so I'm guessing the unit requires a lot of gas to get going, after which it drops down once the cold water is up to temperature. If the unit is attempting to start while the furnace and old gas WH are running, I wonder if the 1" restriction in the piping is causing the low gas pressure? It's all very frustrating.

Code requires that both the water heater PRV discharge line and the furnace condensate line must either terminate to free air outside the structure or into an approved "indirect waste receptor" The termination point of a PRV discharge line must point downward. When extending a pipe through a footer wall we must install a 90deg elbow on the end of the line to turn it downwards. (This is to minimize the risk of scalding water spraying out of the line and hitting someone standing near the point of discharge) Under the IRC when terminating outdoors the line must terminate within 6" of finished grade. Under the UPC it must terminate between 6" and 24" above finished grade. When terminating into the house DWV system or a storm drain system such as you have the PRV line must terminate a minimum of 2" above the flood level rim of the drain receptor, whether that is a floor drain, utility sink or a sump vessel. (The intended purpose of the 2" air gap is to prevent bacteria from entering the line and potentially going up the line and into the heater vessel.) In your case, you could install a tee on the storm drain line and stub a section of the storm drain up slightly above grade, then mount your PRV discharge line pointing down into the open standpipe. Just make sure that the bottom of the PRV line is 2" above the highest level of the riser from the tee. (Note, your 4" line is a storm drain therefore you are not required to install a P-trap below the riser.)