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Author:
rodirv (LA)
I just installed a tankless water heater in a 4200 sq foot home that is built in the shape of a U with one half of the home (south half) having 1 1/2 baths, washing matching and kitchen. The north half has three full baths. I shut the cold water flow into the old hot water tank and disconnected the hot side with no backflow from the hot side as expected. However, I when I turned the water main off then on again, water came at full pressure backwards through the hot side (the line the that had exited the water heater). I shut the main off again and went ahead with the tankless install. After connecting everything back up, the tankless works perfect on all north side faucets, but water does not draw at all through the tank when I turn on any of the south side faucets. I tested the system by shuting the water flow to the tankless. As expected and proper, there was no water flow from the hot side if the faucets on the north side of the house; however, all of the south side hot faucets had full pressure cold water... a clear crossover problem. The only problem is, I isolated all of the sink faucets (two of which are single handle) one at a time as well as the washing machine and the problem continued. I couldn't isolate the tubs but all have separate hot & cold handles so my as understanding is they shouldn't have crossover potential. I don't have a recirculating system, water softener or any other type device that would have a crossover potential. Any ideas at all? There was no problem at all before changing the tank so a preexisting plumbing problem isn't likely, but again, the tank works perfectly just only on the one side of the house (that is the side it is closest to). The middle of the house (U shape base portion) is the living and dining room with no water outlets at all. Any help will be greatly appreciated. Thank you, Rod
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Author:
hj (AZ)
NOTHING you have written gives us any clue as to what is happening. You lost me when you said you turned the main off and then on again, at which time the crossover appeared. WHY did you turn the main off in the first place.
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Author:
rodirv (LA)
I had to shut the main off due to the water pipes from the old water heater being too high. The water heater is in the attic and the pipes were sticking straight up from the attic floor about five feet. I simply cut a two foot section out of each to lower them and used a snakebite couple to join the cut pieces. Before connecting the lines to the new tankless water heater, I turned on the main to test the connections. Since the shutoff to the cold line into the water heater was closed, I didn't anticipate any water out of the hot (outflow) side. However, water started flowing from the open hot outflow side shortly after the main was turned back on causing me to shut it off again until all connections were complete.
What is occurring doesn't make sense. The hot water flow is acting as if the house has a separate hot water source on each side of the house, but there is only one tank. If I now shut the water off at the hot water heater, there is no pressure to the hot water faucets on the north (working) side of the house. However, the south side has full pressure cold water coming from the hot sides of all faucets even when the water it shut off at the hot water heater.
Also, since the water was flowing from the hot water tank outflow line before I hooked up the water heater, it would seen to me that the crossover issue was caused before I made the connection to it. As I understand plumbing, the hot from the water heater line should not have had pressurized water flowing from it back toward the water heater when disconnected. It didn't when I initially disconnected it and the pressurized water only started upon turning off the main, shortening the water heater feed pipes by two feet, and the turning back on the main.
The fact that I got the backflow indicated to me that there was a crossover issue (cold being pushed into the hot water downstream from the water heater), but I've tested all faucets and the washer and nothing checks faulty.
Sorry for the confusion, but the whole thing doesn't make sense to me.
Rod
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Author:
rodirv (LA)
Okay, after fighting with this issue for the better part of a full day, I've learned never to trust a home inspector. I've only been in this house a month and the inspector found one water heater during the escrow inspection. Since the plumbing was acting as if there should be another hot water source on the south side of the house, I got on my hands and knees in the attic and started tracing gas lines. As stated in my first post, this house is 4200 sq ft and all one level so the attic his huge. I found two additional 40 gal water heaters hidden in an area of the attic over a bedroom and bathroom that was added onto the house a few years after the initial portion of the house was built. The attic area was closed off by the original homes roof but for a 2' x 3' crawl space cut into it in a far corner of the south portion of the house. Though the area was not readily apparent and was hard to get to, the inspector never found it and noted in his report that the home only had the one water heater. Worse yet, one of the hidden water heaters wasn't vented properly at all. Fortunately, both look in decent shape and should give me a couple years of service at least. I've lit the pilots that turned off when I had shut off my gas to run my 3/4" line for the new tankless and the hot water is now flowing on the south side of the house. Sorry for the confusing post; I was beside myself trying to figure out what was going on. Good luck to the rest of the folks having issues.
Rod
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Author:
hj (AZ)
That makes absolutely no sense. Cutting the two lines off and then connecting them to the new water heater COULD NOT have done what you describe.
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Author:
SHEPLMBR70 (VA)
It could if one line was hot and one was cold. if the were the lines to the water heater(the old one) they should have been capped.
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Author:
hj (AZ)
They WERE a "hot and cold" line, but they were cut off and connected BACK to the some pipes on the water heater that they came off of. But if you read the rest of his postings, he found the REAL reason for the problem, namely other water heaters which he did not know about.
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Author:
SHEPLMBR70 (VA)
I tried, very jumbled
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