I'm a bit late to respond but I'll give you my input on how our Noritz M-084M is working in Sammamish (Seattle area), which is to say, great! The 8.4 GPM is for a 45 deg temp rise, the lower 5 or 6 GPM is for a higher temp rise needed in Winter. You can find the charts on the Noritz website. I have our unit set to 120 deg and it works well at that setting. Our kitchen is the farthest from the unit, which I installed in the garage attic, and with the temp set at 120 I run the faucet on full hot when doing hand washing of dishes and this is just fine. I find the unit actually works better with COLDER incoming water temp. In the summer the temperature at the kitchen seems to be lower for some reason. The highest load we put on the unit is running two showers at once, which we do on the weekend. It has absolutely no problem keeping up and the water temp stays nice and constant. Our unit is rated at 0.75 GPM to activate, and there is no problem at all to get it running with a bath faucet. Newer units are 0.50 or below. And once it's running it seems like you can turn it down below the 0.75 GPM rate and still get hot water. Go too low though and it will shut off and you'll get the dreaded slug of cold water. This happens very infrequently and has not been any problem. If you haven't purchased a unit and would like to see our installation, drop me an email. I have some pictures or you could come out and take a look in person. Tom

Rheem+appurtenances for $900-$960??... if you say so. Still, Rinnai seems to be "the bar to meet", and I don't see any of them for my app that are even close to 3-figures. But even at your idealized deal + my-labor-is-free-if-I-don't-value-it, I'd still be looking at a 10-year ROI. you can't clean a tank heater. Actually, you CAN, but, the salient point here is: YOU DON'T HAVE TO--ever--hooRAY! More sailing, more skiing, more ____ing! I got a $200 tax credit and a $100 utility rebate... HUGE part of the scam and "unholy alliance" right there--picking everyone ELSE's pocket to goose your lobby... and lobby-ists. There's no reason for some of the over-priced installed costs... So ensconced in the "DIY elite" worldview, I don't even know what to say... is "over-priced" anything over your own FREE labor?... Plumbers and roofers and electricians and carpenters shouldn't be paid? oh, BTW: you did, umm, you know... PULL THE REQUIRED PERMITS for your Rheem job, right? That business about not having hot water in a power outage is more FUD. Look, it's not been a problem in 7 years, and when the power goes out, my first instinct isn't to jump in the shower. It might mean I would go over to a friend / family member's home for a shower... Lulz... you've never lived in a HVHZ... and you never should. Friend? Family? I'm not talking about a power outage you hear about on TV, I'm talking about a power outage you can see from SPACE! When the eye of Wilma passed over my zip code, there was no power for *45 miles* in any direction! (14 days at my house) But medical personnel, cell phone technicians, UTILITY LINEMEN, cops, firefighters, paramedics, propane distributors, and parcel delivery peeps (among MANY others) still had to report to work. Just how smelly (and UNsanitary) do you want your nurses, docs, and x-ray techs? No salving showers for the out-of-state lineman working 15 hours a day/7 days a week, to reboot civilization? Sorry, NO SALE on that tankless EXCUSE. Natural gas infrastructure, largely underground (and therefore a nightmare in serious earthquakes), is unaffected by windstorms. This makes it an extremely valuable resource during the "bootstrapping" process... why put something on the end of the pipe that blocks access? At least keep your TANKed WH Y-plumbed over to the side... just in case. ... if it went on a long time or I could just heat water on the stove. A GAS stove... with electronic ignition? ;') I also like the fact that I'm not wasting energy and contributing a little less to environmental problems. Did someone add vodka to the Kool-Aid? You're blithely ignoring the extra energy and POLLUTION necessary to build tankless. Suggest you go "in-depth" on the chemical wastes just from printed-circuit board manufacture... then on to the additional exotic materials and tech NOT found on conventional WHs.

Mechanical Codes require flues or chimney to be resized if appliances are removed and some appliances are left 'orphaned'. It is likely that your home inspector uncovered a Code violation and unsafe condition because of this 'orphaned' water heater. The simplest means to correct the problem is usually to replace the water heater with a new one and have that new water heater direct vented or power vented to the exterior. This should be done at the current owner's expense. Contact your local mechanical code inspector for details.

HI, I'm not sure what was used to submit or edit the original question, but the entire post wasn't very clear. I also don't know if this is being asked by someone in the USA: Codes vary by country. I'm going to give you some general answers to the questions that I think you are asking: 1.) Don't "rig" a heater to use it in a way that it wasn't intended. If it was designed for outdoor use, don't use it indoors. 1.A) Don't even think about rigging the venting. Don't substitute materials, don't improvise. You will find yourself dead. 1.B) Don't even think about rigging the gas. Again, you will find yourself and your neighbors dead. 1.C) Don't even think about rigging the electrical. You will find yourself dead 2.) There are ways to increase the capacity of a single tankless heater by using multiple units. The units must be made for this purpose. You must have the gas supply to accommodate such an install and it does not make sense to use multiple small units when a single larger unit is available. Again, don't even think about stringing together multiple units without them being expressly designed for that AND doing the work by the book. If you currently have a 40 gal tank, I can't imagine you would need more than ONE 200k BTU/H unit, which is as large as they typically come. 3.) There are ways to use a primary heater (for example your 40 gal tank) and a point of use heater. We do this when a master bathroom is at one end of a house and the tank heater is in the garage (really bad design) but it's not common. What you are describing though sounds poorly thought out. 4.) The setup you are describing would not save energy or operating costs. 5.) A competent plumber can address your needs - but isn't going to help you rig a system. If the issue is running out of hot water, then a larger tank heater can be the most effective way to resolve that issue. If the issue is lower operating costs, then a single tankless gas unit or a hybrid electric tank unit can be a good choice (but come with higher up-front costs). Again - I can't say this any more clearly: Do not use a heater in a way that it wasn't intended. Do not improvise or substitute materials on the venting, gas or electrical supply. Do not string together multiple units unless they were designed to operate that way. There are installation and use manuals available online for any of these heaters. Follow the design and installation instructions. If you aren't very familiar with plumbing and water heater installation, use a professional.