I think T-Bones is over reading the info. NO, I am not wrong, and you are only 1/2 wrong. So I am still ahead. LOL I got my information off the website: http://www.blueflame.org/datasheets/combustair.html If you will goto that site and scroll down toward the bottom and look under the heading, " Air Supply to a Furnace Installed in a Small Utility Room or Confined Area you can read exactly what I posted. It came from the blueflame people themselves. It tells you how to do it and figures your hole for you and everything. T-Bones is only half right in his post above, where he states, Provide additional ventilation of at least 2 sq/in per 1000btu/hr of input for any additional fuel burning appliances used at the same time. If you read the statement, you clearly see that the 2 inch hole is there because you are operating 2 appliances. If you had 3 heaters running, you would use a 3 inch hole per 2000Btu's and so on. I stated the rule of Thumb and I will state it again. For reference: The rule of thumb is 1 sq. inch per 2000btu's of heat for an air intake in a tight greenhouse. Most greenhouses are only going to have 1 heater running inside them. The hobby houses on this forum will use small heaters at best. Once again more references for those that need proof. Websites: http://www.greenhouses-etc.net/heating/nv_gas_heaters.htm They show a 20,000 btu heater, and recommend a 3inch pipe. We can work out the math, 3 in x 3 in is 9 square inches. 9 x 2000= 18,000 btu. Their btu rating is on the higher side. They are saying about 1 sq inch for every 2222 btu. And no this is not why people get killed. People get killed because they dont read directions. They dont follow rules and they dont do their own research first, and another thing, you can have all the rules and rule books in the world, but if you don't apply a little COMMON SENSE every now and then, your going to get hurt anyway. Please, lets not shoot each other down. If you have a problem with someones information, just ask them about it. I been running my greenhouse on facts for 15 years now, why on earth would I want to tell you something wrong or incorrect. I dont just pull this s__t out of the air and type it on the screen.

Hi mongo- Thanks for your thoughts. I agree that the small pump and loop would be best, but I think too difficult at this point. Here's the situation: bathroom is over a VERY shallow crawl space (used to be about 5" between joist and dirt, but when we gutted the space my DH spent many sweaty days shoveling the CLAY soil out through a hole we cut in the wall. Ugh!) The only access to underneath the floor would be if we removed the tub and cut out the subfloor. Even then, there's only about 18-24" under there. The supply used to run in the exterior walls, and froze last winter. We (DH) rerouted the supply through the attic space (one story home). He ran it right along the sheetrock, and insulated the cold lines with that grey split stuff against summer condensation. Then he created a sort of "tent" or "tunnel" over both sets of pipes with that aluminum faced bubble-wrap type of insulation. All foamed tightly in place. On top of that is two layers of pink finerglass batt. It's certainly better insulated than it was before. Pipe is 3/4" PEX. At the interior bathroom wall, it turns down to supply shut-off valves accessible in the bathtub control panel. From there it runs under the bathroom floor, on the warm side of rigid insulation foamed tightly to the joists. I actually just got off the phone with a tech guy from one of the tankless on-demand companies. He says that the tankless option is do-able, but we'd need such an upgraded model that it wouldn't be worth it for the 30 seconds or so we'd save waiting. The only place to put it would be in the closet by the shut-offs (since that's the closest access we have). And since there's no way to add it to the sink-only plumbing (I don;t think: see below) it would have to be sized for the GPM the shower demands, otherwise even when it's not heating the water, since the hot water is running through it, it would reduce the flow at the shower too much. Since we have a showerhead AND handshower that sometimes run simultaneously, that would not do. And the higher GPM models are just too pricey. I was thinking I *might* be able to swing $125 or so by next fall if I saved. not $500 certainly. Our bath remodel and some medical emergencies have really drained us, I'm nervous about even buying fuel oil for the rest of the winter! The only space and access at the vanity itself is a 4" space between the wall and the back of the drawers. The vanity is all drawers, and was custom made, so we can't/won't modify it. I don't imagine any of the cheap heaters are like 3" deep? So, I will probably have to learn to live with it. Not a huge big deal. The shower and tub take very little time to warm up (higher GPM I guess) so its really the sinks that are the issue. We'll probably just live with it. Thanks!

Gary: I'm building a new house next year where this 6-head shower will reside. It's the one big indulgence I'm allowing myself. The house itself will be super-insulated and airtight to the point that it'll require no more than 12,500 BTUs to keep the house at 70F when it's -20F outside. I'll basically be able to heat the house with a Zippo lighter, although I'll be heating the place with wood. The shower that I'm allowing myself will be using well water, coming from and returning to my land, which will be preheated both by a loop from the woodburning boiler stove that heats the cottage as well as by a substantial GFX drain heat recovery system to get the Delta T somewhere between 20 and 30 degree (depending on the time of year.) I'm sorry you're skeptical about the performance specs of the GFX, but that's your issue, not mine. I'll also be using a pair of incredibly energy efficient condensing tankless water heaters to heat the pre-heated shower water to the final desired temperature. I've done the math now and have calculated that to take two 30-minute showers per day, utilizing all six shower heads going full bore (450 gallons per shower!), each will require an average of 1 gallon of propane costing approximately $2.40 per shower. This is less than the smallest Starbuck's Latte you probably throw back on your way to work. I'm hyper-aware of my carbon footprint. And I'm willing to bet that the footprint caused by my home will be less than the one caused by yours. I just happen to place a high priority on having a really, really great shower. Bottomline: The calculations you provide are erroneous and based both on a lack of information and a number of false assumptions. More importantly though, your perception of what I'm doing is really myopic. You should be concerned about ones NET carbon footprint, not about any one individual indulgence. Don't be so quick to jump to conclusions. You just end up looking foolish. John

Fixing the running toilet fixed the usage problem and the softener appears to be functioning perfect, which I guess begs the question, is it OK to leave the check valve in? It does not appear to be restricting flow in any way (valve shows maximum SFR to date of 13.9 gpm) and I don't think it is creating any back pressure. Wouldn't the check valve actually prevent any back pressure from reaching the valve and resin tank and in turn protect the resin tank and valve? Say for instance that the expansion tank was malfunctioning for whatever reason, and the water heater kicked on and created a brief expansion that drove the psi up to say 150 psi and that back pressure pulse was pushed back to the check valve since the expansion tank didn't work correctly. Wouldn't the check valve slam shut and prevent this back pressure from reaching the resin tank and valve? If the normal line pressure on either side of the check valve is the ambient 60-70 psi of the system under normal conditions and a back pressure pulse of 150 psi comes from the water heater side of the installation, isn't that precisely the set of conditions that would cause the check valve to close and keep the pulse on the water heater side of the system? I realize that with check valve in place and the theoretical malfunctioning of the expansion tank, the pressure pulse will seek some method of escaping which could cause damage somewhere in the house like a faucet or toilet, but at least it will not have blown the resin tank or destroyed the control valve, correct? I hope this rationalization makes sense, but I'm not sure that I have done a very good job of positing my questions or explaining the scenarios. Oh well. Take a swing at it if anyone feels like it. I am interested to hear some opinions on this one. I'm thinking more potential bad will come from disassembling a functioning, dripless install than from keeping the check valve in place. Thanks. Drew