Okay, finally I have success! I'll detail what I did as it might save someone a lot of headache. First off, hot water pipes are thinner than cold water. I think cold water is type M and hot is type L or vice versa. No matter how many times I look that up, I still forget! Anyway, I got pretty good at cutting the thick one but was having MAJOR difficulty cutting the thin one. To make a long story short, I had to use a hand held key saw. Annoying, slow but that worked. Next, stick bread in the lines on both sides to block the water. You think you get all of the water out of the line, but you don't. With water in the line, soldering will be impossible. You'll have to heat the joints three times as long and the solders won't be good. I had leaks by not following this. A step which I knew but still didn't do. Stupid on my part. Okay, no more leaks. Now, I'm supposed to bleed the lines. Although my house was built in the 1930s, we added a large addition and the house is pretty new, including the heating system. It seems that the plumbers are no longer putting bleeders on the line. Mine don't have any. No problem. I should just open up point 1 in pic 2, and the valve on point 9, pic 1 (which you can't see) then open the garden house valve on line 1, pic 2. When the water flows out smoothly with no sputtering, the air is out, right? Well yes, but things just weren't working that way. I did everything I just said and water came out. Within 10 seconds, however, all the water came out and it just dried up! Uh, is that supposed to happen? Confused, I shut the line and waited about 30 minutes while I did other things. I came back and tried again. Same results!!! I had about enough of this plumbing project. Looks like it won and I lost. After about 10 successful projects, I was going to have to call in a plumber. I tried getting the job taken care of with my normal service contract, convinced that it was just a lack of knowledge on my part. I was told that since it was the weekend and they weren't sure the project fell under my normal service agreement, they might have to bill me...at the more expensive weekend rate...of $165 per hour!!! I quickly told the lady I'd figure it out myself. Searching this site, I found the answer. I did everything right except one thing. You have to continually add water to the line so that it keeps flushing the air out. You do that by flipping the little handle on point 5, pic 2. That automatically ensures that the pressure in the baseboards remains at the setting on the reducer by adding water when need be. However, if you open it manually, it will just let the water flow (also pushing the air out with it). If there's air in the line, the pipes aren't going to get hot, so you've gotta get the air out. With each bucket of water I let flow through, more of the line got hot. Three buckets of water later, the water was flowing smoothly and I had heat! Note that by me doing what I did, I introduced air into another zone, so I had to repeat the process for that zone as well. No biggie. Three more buckets later, that zone was working again! Now I don't know if there's a way to work on one zone while not affecting the others. I'll have to examine what I did a little and see if there's a sensible way of doing it. Anyway, hopefully this helps someone.

I wanted to report back and thank all the folks here for their advice. We did end up using a 2" PE pipe. The interesting thing was that my plumber had never used it. Neither had 4 other who I got quotes from. They were willing to use PVC or PEX but other than my plumber, no one was even willing to look into PE. The city inspector had never seen it and had to check the california code book to see if it was even approved (It is). The local plumbing supply stores (big box and speciality) did not have it or have in the length that I needed (280ft). So the plumber took his van up to San Francisco to buy it. The plumbing supply store also told him that he has to use a special machine for the joints that he can rent but he had to get trained before he could do that. So my plumber did get trained, rented the machine, got the pipe. It took him a few hours to lay the pipe, wrap some 18 guage wire (CA code for non-metal service lines). He connected to an existing copper for a cottage, connected to a landscape faucet, and the main house. The cost was much more reasonable than Copper. We are in middle of a remodel, so we did not need a special permit.. just an inspection. Saga over.

"In the end, I would make the decision based on the estimated risk the pipe becoming energized." Chris, There is legitimate discussion about the need to bond the hot water to the cold at the water heater since until recently it was connected by other means and it isn't specifically called for in the NEC. Your statement that "They probably already are bonded through a shower valve in the house" leaves open the possibility that they aren't - which is the whole point here. Bonding is not the same thing as using the piping for a grounding electrode. The NEC is very clear that all piping must be bonded to the electrical system. It's not an option to decide if you want to bond the piping to the electrical system. Most certainly you don't get make a decision that "you don't think it will become energized, therefore you aren't going to bond it" as suggested by your last sentence. Think of the implications if an un-bonded water pipe comes in contact with an electrical wire and then you go to take a shower, or do dishes, or any number of other things. If it's bonded to the electrical system, it causes a breaker to trip. If not, everything it touches is energized.

This post might be old but id like to respond. HI, Big Bias I'm seeing here... I would like to show some transparency so people know the actual costs. I would also like to note that i'm not including Markup to pay for things such as both types of insurance working and worker, Municipal licencing, Over head for a shop, Gas and insurance for a vehicle, the time it takes to order products as well as picking up/ delivering products. Expect a mark up of 26-37% on everything to pay for these items. If it's a Small one man company out of their home figure on the low end. If it's the largest plumbing company in the district expect to pay more. On the flip side they may get a bigger discount on the unit and hide that mark up in the unit it's self. My location is Alberta Canada, So keep in mind CND$$$. A typical 40-50Gallon Natural Draft hot water tank is 36-50k BTU's . A Rheem or Renai or Navian tankless is typically 140-205K BTU's . The Tankless will need a larger gas line. Usually needing permits. In my Jurisdiction The inspector gives a 4 hour window for inspection. So you'll be paying for a plumber for 4 hours. On top of that Tankless units DO NOT use the same venting as a Natural draft old style water tank. Thus a Venting inspection by the same inspector. Permit needed. So you will be changing two Major components of your homes "gas" and "venting" systems. Typical install time is about 4-6 hours. This includes, Turning off the water supply, Draining the house and tank, Unhooking the venting, Unhooking the old water supply. Then Mounting the new unit to a wall or Optional Metal rack carrier, Running new water supply lines complete with new valves and possibly a new Humidifier valve if the old one was above the hot water tank. Once the new lines are run, then they can Cap the old Vent. In some Jurisdictions this vent may be removed all together with a general contractor removing and capping the roof. Again more permits needed in this case. After the old venting is capped. then running new venting out of the side of the house. which has to be 12" from other venting or 3' from any opening door window or gas meter. If it's an older home you'll need to hire a Coring contractor to Core a hole through the Cement foundation. If the home uses TGI joists you can typically exit through there. Once the venting is complete the contractor can move on to the gas line. Cutting gas to the home for up to a couple hours Hopefully using "lock out tag out procedure" IE locking the riser while they work. They will open the outside of the gas line close to the meter Then Purge. Meaning to leave it open to air for 10 minutes. Some companies use a manual pump from the inside to push the gas outside. Once purged properly the contractor can start to take the gas line apart to add a tee. Remember he was supposed to "Size the gas line" at the time of Estimate to make sure your home has a large enough line for the added BTU's If he doesn't show the inspector this Calculation he could instantly fail inspection even if he did a good job. Most contractors will install a hard Tee then run Flex CSST Gas line or "Gas Tite" similar product. Once the gas is hooked up they do another purge the other direction. removing air from the line from the outside in. once gas is at the fixture it's time for commissioning. another 20 or so minutes till he's done. In my Jurisdiction the venting materials are to be Gas 636 PVC piping minimum. In multi unit dwellings it will need to be a higher spec. Cost of venting materials depends on length but the average is about $210 2" Double that for 3". Parts, correct type of glue Primer and glue. (the inspector checks), 2 45's 4 90's , 2 couplings, TY, 4 lengths of pipe. Seems rare to have an up and out easy unit. but costs obviously for that $60 or so depending on elbows needed. Gas permit $212.65 Materials gas $85.00 15' CSST, CSST adaptors, Nipples, Black 1 1/4 x 3/4 tee, Tape, jet lube, Materials Venting $210 4" B-vent Cap, 636 pvc piping & elbows Optional Rack $310 1/2" Plywood and screws $32.00 6 hours labour $510 Inspection time say we're lucky and only wait 2 hours $170 Owner supplied Tankless install 1219.65 Navian NPE-240A Wholesaler price $3044.22 Including Service kit. Some companies may get a higher discount through volume. Navian NPE-240A Amazon price 2800.00 No service kit https://www.amazon.ca/Navien-NPE-240A-Premium-Condensing-Tankless/dp/B00FAMAB2U/ref=pd_lpo_sbs_60_t_0?_encoding=UTF8&psc=1&refRID=P40Z2FYMVNSYE4DJ1A24 Also don't be fooled when it says 1/2" gas line the actual fitting is 3/4" it's just saying they have a special valve inside that allows for lower gas flow but in turn the burner does not run at full capacity. Total Canadian Dollars $4263.87 Transparent Fair pricing