"How does an electric dry pull a lot of air?" Mike: Of course there's a fan inside the dryer. All clothes dryers, electric or gas, pull a lot of air from the surrounding area, run it past the heater (gas or electric) to heat it, through the drum of wet clothes and out the dryer vent. Regarding the furnace: Anything other than very minor leaks in the return air system on a furnace (which are usually canceled out by minor leaks on supply plenum) are a problem. You can have back drafting of the furnace - far worse than back drafting of the water heater because it's more CO (more btu/hr input) and because that means it's pulling the CO into the return air and circulating it in the house. "I would not trust any contractor to know the local code especially where a mistake could cause a big safety issue"... umm ok. To begin with that's not really the issue - since as I said, the issue is that Lowe's WON'T do the job. But that's really an absurd statement because virtually every job, be it electric, HVAC, Plumbing or even many carpentry jobs depend on the contractor knowing code to do a safe installation. If we can't start with that assumption the building trades would come to a screeching halt. I'm not naive... I do know people make mistakes and/or are unqualified. But the people who do this for a living and have their work regularly inspected by local authorities and who's livelihood is dependent on being able to be licensed, bonded and insured are in a pretty good position to know local code. Besides, killing your customers is a big civil liability, potentially a criminal liability and really bad for business. It's far more likely that the average DIY installer would make a serious safety error. The OP is very aware of the makeup air issue. He's going to point that out to the contractor so it's not overlooked. As far as we know, this has been an acceptable situation up to this point with makeup air grills in the outside wall and floor. Nothing has significantly changed since the original design. A contractor is going to confirm the makeup air situation meets code and then install the heater. He may even inspect the current heater for evidence of backdraft. The real issue is a broad warning in the manufacture's installation instructions that, while is important to bring to installer's attention, is too broad. (again, how near is "near"? Is that 24"? is that in the same room? is that in the same dwelling unit?) Lowe's had no choice about following this prohibition because explicit manufacturers instructions are binding if not counter to local codes. If the instructions said not to install the heater in a room that was painted white, it would be just as binding.

Thanks for the info. Can we have an old style gas water heater (in the attic) AND tankless water heater downstairs servicing the same house and gradually phasing out the fixtures (room by room) with end result of eliminating the old gas water heater after remodel complete? This post has helped me realize that my main desire is to try to do this in phases rather than one job (which I'm sure would be cheaper.) For one reason, the smaller jobs help us evaluate the contractor and decide whether we want to continue using him (he gets to evauate too). It also helps us keep from having so many "change orders" before job is done as we learn more about our 77 year old house. (think I will cross post this in the "old house" forum as well) background: I think we are committed to going forward because we LOVE our neighborhood but neighboring homes are old like ours so besides prices being quite high though footprints are small (in center of major metro area), we are afraid we would buy another old home that was in worse shape than ours and would still need to do work.

What you have there is a very desirable feature, and one that I highly encourage my clients to allow me to install. Years ago when they still did laundry in Hot water it was common for water heaters to be set at 180 or 190degF, especially if the water heater was supplying a dishwasher because the health codes require 180degF water for the sanitizing rinse. The Medical profession says infants, children and ppl with sensitive skin can be seriously injured by water temps exceeding 130degF, so the Plumbing codes were ammended limiting the temperature of domestic hot water to not more than 125degF. Now most laundry detergents work fine in cold water and nearly all domestic dishwashers have a built in booster heater to provide the 180DegF sanitizing temp. (When you turn the "power saver" switch on it disconnects the booster heater to save energy). Within a short time it was realized that trained plumbers could be relied upon to set the water heater thermostat to the code prescibed 125degF, but there was no way to prevent the homeowner from coming behind the installer and turning the temperature up, so in order to protect themselves from future liability most domestic water heater manufacteres installed thermostats that only go to about 140degF, and instead of marking the temperture on the control knob they just put an index at 125degF, indicating the correct temp to operate the heater. There is only one small problem with that solution. The human body temperature averages 98.6degF and most ppl like their shower slightly warmer than body temp, which means an average shower is 105 to 115degF and some even like a Hot shower which is in the range of 120 to 125degF. The problem here is that back when the water heater was firing at 180 a typical shower was approximately a 60/40 mix of Hot & cold water, but once the source temp at the water heater was turned down we now have approximately a 95/5 mix of hot & cold water. Keep in mind that even with a code required 2.5gpm shower head a 10minute shower consumers 25gal of water, and if that water is coming from a water heater that is only producing 125degF water, it is very easy to run out of hot water before the shower is completed. Now add to that the fact that most new homes have at least two if not more bathrooms and it is quite common for two or more ppl to be taking a shower at the same time so the supply of hot water is critical. The standard solution today is to install bigger & bigger water heaters, in fact, where a three BR house previously had a 40gal water heater it is not uncommon to see an 80gal heater or even two 60gal heaters in homes today. Now you have to understand that while you are drawing the 125degF water off the top of a typical water heater, that heater is also being constantly filled with 35 to 55degF cold water from the bottom, and as that cold water enters the tank is dilutes the stored water, which results in loosing temperature in your shower quicker. The WATT's tempering valve is actually a mixing valve, so you can turn the temperature up on the water heater and as the super heated water enters the Watts vavle it is mixed with cold water so the output from that valve is at the code max of 125degF. The end result is that you have 25% to 35% more usable hot water from the same size of tank. Now in regard to your original question. I cannot see how it is all hooked up at your house so I cannot comment on the second cold water line, but I have attached an illustration of how we typically install a tempering valve and I am certain you can connect it with just one pipe coming down from the ceiling. The only thing you have to remember is, the horizontal line from the cold water supply to the tempering valve must be connected to the coldwater line before the water heater main water shutoff valve.

DISCLAIMER: I am not an electrican. There should not have been anything more than low leakage current in the water pipes. Some common leak sources are electric water heater, washing machine, garbage grinder, and dish washer. If this is an older house, it may have been wired expecting the plumbing to provide grounding when the intended path was less than perfect. Older wiring did not have the 3rd ground wire and depended on a metal cable shield to provide this path. This shield was supposed have been well bonded to each box that the circuit passed through. Sometimes, these bonds were less than prefect. The plumbing ground was broken when a piece of plastic pipe was inserted at the entrance. Maintaining the plumbing ground is important. The codes in my community require a grounding strap around the water meter to shunt the current around the meter and to insure a ground when the water meter is removed for service. Water meters do not like electrical current. Our town changes all water meters every 10 years for maintence and calibration. The grounding shunt in my house is a piece of conduit securely bonded to the water pipes (which are copper). You should measure the voltage of your leak. It may be at a dangerous level. In fact, there should have been no sensation. Find the culprit and fix. Luckly, you have found a potentially dangerous condition before any harm was done. DISCLAIMER: I am not an electrican.