Dan87
New Member
Hello all!
Long time reader, first time poster. I recently re-plumbed my entire house, supply lines, drain system, all new faucets and fixtures...the works. This was relatively easy since all of my plumbing is right on top of each other straight up through the house, although still a lot of work never the less. Everything works perfectly except for one detail. The hot water back tracks into the cold supplies, not when in use, but when dormant. I live alone, so not much water gets used, but when the lines get flushed for a few seconds (3-5 seconds) temps are normal. When I get home from work (water hasn't been used in about 10 hours), the cold supply going to the water heater is hot all the way back to the PEX manifold. Now, I originally thought this was possibly due to the water heater being so close to the manifold, but my oil burner supply is doing the same thing, and that is located on the other side of the basement, about 25 feet of piping away. The only reason I can surmise is because I have two independent water heating systems feeding the same manifold? The reason for this is the fact that my oil burner type is a "summer-winter" hook-up, and needs water flowing through it all the time, and needs to maintain a warm core temp all of the time (or so I've been told and research has told me).
So, the PEX manifold utilizes the bottom 3/4" inlet for the main feed, then the top 3/4" ports are used for the water heater in and out. The oil burner is fed and brought back through the standard 1/2" distribution ports. I know, this means I'm using both oil and electric to heat my hot water, but my logic is that since the water heater is using 3/4" pipe and the oil burner is using 1/2", more of my hot water will be pulled from the water heater than from the oil burner, allowing the oil burner to still run as needed. This being my first summer in the home, I think I burned about an 1/8" of a tank of oil, which works for me. While I'm on the topic, I debated on using the water heater as a "pre-heater" to the oil burner, which would theoretically mean the oil burner would fire up far less frequently. However, not knowing if that was a good idea I didn't do it that way. Further discussing the topic with other people, they noted that bringing in water at a temp only 10-20 degrees below what the aqua stat is set for, may cause the oil burner to not fire long enough to burn properly, causing excess carbon/soot build up in the unit. Any thoughts on this are welcome as well!
Anyway, back to the back tracking. Both the oil burner and water heater have thermal expansion tanks right near them (as seen in the pic of the water heater), and I checked it's pressure prior to installation and it is correct. While installed, you can hear that it is mostly air inside when you tap it (and some water at the top). The bottom line is all of my cold feeds off of my manifold get warm, and the first 2-3 seconds of cold water at a tap is warm, then gets cold. If you run the hot side of a faucet for a few seconds to a minute, and feel the cold feeds to the water heater or oil burner, they immediately get cold, as cold water is now flowing through them. So, it doesn't seem as though the water is "back flowing" as I've heard so much from people, as it is "back tracking", because it's happening when nothing is in use, and corrects itself as soon as water is flowing. The back tracking warmth actually heats up the cold side of the manifold and warms up all of the cold feeds for about 12 inches off the manifold. Any input on this would be much appreciated. Sorry for the lengthy post, but I needed to be thorough. Thanks!
PEX manifold and GE Geospring water heater
PEX Manifold Port Usage
Cold water supply to water heater that gets hot
Oil burner cold supply that gets hot
Long time reader, first time poster. I recently re-plumbed my entire house, supply lines, drain system, all new faucets and fixtures...the works. This was relatively easy since all of my plumbing is right on top of each other straight up through the house, although still a lot of work never the less. Everything works perfectly except for one detail. The hot water back tracks into the cold supplies, not when in use, but when dormant. I live alone, so not much water gets used, but when the lines get flushed for a few seconds (3-5 seconds) temps are normal. When I get home from work (water hasn't been used in about 10 hours), the cold supply going to the water heater is hot all the way back to the PEX manifold. Now, I originally thought this was possibly due to the water heater being so close to the manifold, but my oil burner supply is doing the same thing, and that is located on the other side of the basement, about 25 feet of piping away. The only reason I can surmise is because I have two independent water heating systems feeding the same manifold? The reason for this is the fact that my oil burner type is a "summer-winter" hook-up, and needs water flowing through it all the time, and needs to maintain a warm core temp all of the time (or so I've been told and research has told me).
So, the PEX manifold utilizes the bottom 3/4" inlet for the main feed, then the top 3/4" ports are used for the water heater in and out. The oil burner is fed and brought back through the standard 1/2" distribution ports. I know, this means I'm using both oil and electric to heat my hot water, but my logic is that since the water heater is using 3/4" pipe and the oil burner is using 1/2", more of my hot water will be pulled from the water heater than from the oil burner, allowing the oil burner to still run as needed. This being my first summer in the home, I think I burned about an 1/8" of a tank of oil, which works for me. While I'm on the topic, I debated on using the water heater as a "pre-heater" to the oil burner, which would theoretically mean the oil burner would fire up far less frequently. However, not knowing if that was a good idea I didn't do it that way. Further discussing the topic with other people, they noted that bringing in water at a temp only 10-20 degrees below what the aqua stat is set for, may cause the oil burner to not fire long enough to burn properly, causing excess carbon/soot build up in the unit. Any thoughts on this are welcome as well!
Anyway, back to the back tracking. Both the oil burner and water heater have thermal expansion tanks right near them (as seen in the pic of the water heater), and I checked it's pressure prior to installation and it is correct. While installed, you can hear that it is mostly air inside when you tap it (and some water at the top). The bottom line is all of my cold feeds off of my manifold get warm, and the first 2-3 seconds of cold water at a tap is warm, then gets cold. If you run the hot side of a faucet for a few seconds to a minute, and feel the cold feeds to the water heater or oil burner, they immediately get cold, as cold water is now flowing through them. So, it doesn't seem as though the water is "back flowing" as I've heard so much from people, as it is "back tracking", because it's happening when nothing is in use, and corrects itself as soon as water is flowing. The back tracking warmth actually heats up the cold side of the manifold and warms up all of the cold feeds for about 12 inches off the manifold. Any input on this would be much appreciated. Sorry for the lengthy post, but I needed to be thorough. Thanks!
PEX manifold and GE Geospring water heater
PEX Manifold Port Usage
Cold water supply to water heater that gets hot
Oil burner cold supply that gets hot