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Thread: Sediment in hot water lines with tankless heater

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    DIY Junior Member
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    Default Sediment in hot water lines with tankless heater

    I have been having problems with sediment (looks like large pieces of sand and tiny rocks in varying colors of brown and black) accumulating in my faucet aerators and shower heads. I installed a whole house filter at the water main thinking that the water coming into the house was simply "dirty". Then I cleaned all the aerators in the house, and even decided to clean out the lines for my washing machine. That's when I realized the problem is with my hot water only, because the cold line to the washer was super clean but the hot water line was full of the sediment. It is so bad at this point that I am cleaning out aerators on a weekly basis, otherwise there is no pressure or hot water at the faucet or shower head. The washing machine keeps giving me an error code becaue the hot line is full again and no hot water is getting to it. I have an electric tankless water heater and I thought that there wasn't supposed to be any sediment with a tankless heater. My home is less than five years old and I live in Tucson, Arizona. The water has been tested and the hardness is less than 10. Anyone have any idea what is causing this problem?

  2. #2
    In the trades Dana's Avatar
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    Accumulated crud in the lines keeps moving?

    Deteriorating galvanized plumbing?

    Whatever it its, it's not the tankless, which has extremely low water volume. It might lime up and restrict flow in hard water areas, but it can't develop a layer of sludge the way tanks sometimes do.

  3. #3
    In the Trades AAnderson's Avatar
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    Default sediment from tankless hot water heater

    All tankless manufactures recommend softeners if the water has more than 11 grains of hardness (roughly 210 ppm total dissolved solids). Calcium will precipitated out in hot water which is why you are experiencing the debris you are in appliance pre filters and aerators...

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    Macintosh Computer Consultant/Tech macmikey's Avatar
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    Default Have Rinnai Tankless and sediment also

    My plumber said it was from the old tank heater and the crud it created.

    He comes out, on schedule, to flush the system, run a vinegar solution through it and then flush it again. He also replaces my whole house filter and maintains the faucets for me as well.

    I go around about every 2 weeks or so and clean out all of my faucets and other filtery kind of things to prevent blockages.

    The routine maintenance is required for the warranty on the Rinnai or you may not get service on it. It does not reduce the crud, but does guarantee that the heater itself is not going to be damaged by it.

    Mike

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    In the Trades AAnderson's Avatar
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    Quote Originally Posted by macmikey View Post
    My plumber said it was from the old tank heater and the crud it created.

    He comes out, on schedule, to flush the system, run a vinegar solution through it and then flush it again. He also replaces my whole house filter and maintains the faucets for me as well.

    I go around about every 2 weeks or so and clean out all of my faucets and other filtery kind of things to prevent blockages.

    The routine maintenance is required for the warranty on the Rinnai or you may not get service on it. It does not reduce the crud, but does guarantee that the heater itself is not going to be damaged by it.

    Mike
    Mike, define crud? Do you mean small white particles that looks like broken sea shells? This is calcium that has precipitated out of solution under heat and pressure, a problem is you have hard water. A whole house filter will not remove dissolved solids.

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    DIY Junior Member 4fuzzies's Avatar
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    I'm a little worried since this thread was posted in 2009 and there doesn't seem to be a consistent answer. We too have the sediment in our hot water lines that looks like sand and up to 2mm sized pieces of mineral. We too were convinced to put a water filter on the incoming water. This did nothing for the problem and just killed our water pressure. It seems to be worse in the winter, we clean the shower head 3 times per week as apposed to once a month in the summer. Our water heater in a natural gas powered rinnai tankless that was installed in 2009. Our heat unit is an Apollo hydroheat system. We had no problems from 2005 when we moved in, until the summer of 2010. Then we lost hot water. The plumbers that put in the rinnai came out and cleaned the in line filter and the faucet aerators. We thought at the time that the sediment was from when the city changed the meters on the water lines. The problem went away until fall 2010 when the heaters kicked on. That's when we were told we need the whole house filter. It fixed nothing. We still have sediment in the lines that makes me feel like when I run the bath for my kids, I'm not getting them any cleaner. We call out plumbers... they say its the Apollo unit. We cal out hvac guys they say either they can't touch the Apollo units or its a plumbing problem, call a plumber. We have had several different companies come out. No one has an answer. We have to run the sink in the bathroom if we want to take a hot shower, otherwise because the lines and showerhead are so plugged, not enough water flows through the rinnai to turn it on. We did not have any problems the first winter after getting the new rinnai tankless. For what it is worth, our house was also plumbed using the now illegal Quest pipe. Please help. This thread is the closest thing we have found to an answer in 2 years.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Have you demineralized the tankless system? It's fairly easy if it was setup properly with the appropriate fittings, otherwise, it can be a pain the first time (assuming you install them now). This involves pumping a weak acid solution through the thing for a period of time to disolve the minerals. Depending on the hardness of your water, your total water use, and how hot you have the tankless set would all affect how often it needs to be done. The internal passages could be restricted a lot, and the minerals also act like an insulator. Depending on the heating, some could break off during use and may be the source of the mineral chunks.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member 4fuzzies's Avatar
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    Thanks Jadnashua, I will ask the installing company when they call me back. I forgot to mention that we did have 1 plumber (who was out for a busted pipe) tell us how to flush the water lines by draining the lines and then flushing water into them and turning the faucets on 1 at a time. We have done that 4-5 times since December. The first flush maybe seemed to help some, but I have not really been able to tell any detectable difference with the subsequent flushes.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    That will only dislodge or flush loose stuff...that is totally different than what I'm talking about. Basically, you turn the heater off, disconnect the lines (or if you already have flush valves installed, switch them to flush position), then you use a pump and a hose and a couple of buckets to run acid through the heater. This disolves the caked on mineral deposits that are in the thing. WHen done (might take a hour or so), you reset the lines to 'normal' and flush the thing out from the acid, then you can turn the heater back on. The exact procedure depends on what fittings and valves you have, and how you need to make it all work. From what I remember, Tucson doesn't have the greatest water (really hard!), so you should plan on doing this probably at least once a year. Someone who knows how to service this type of heater will be able to advise you on how to maintain it properly.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member andream's Avatar
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    ryguy, I wonder if you have ever resolved this issue, or if anyone has figured out how to.
    We have 2 Noritz tankless water heaters in a 5 year old house. Over the past few years we have had many problems with water pressure and clogged aerators. We finally had plumbers install flush kits on our heaters and have since flushed them 3x, 2x with vinegar and the last desperate time with CLR. Still there is sediment in the hot water lines. I contacted Noritz and they suggested we need a water softener. We really don't want to take the minerals out of the water or put in an expensive purification system. We are considering a post-heater sediment filter and wonder if anyone has done this and if it will work. I don't mind cleaning out the sediment once in a while to stop it from reaching our dishwasher or washing machine which has resulted in some expensive repairs.

  11. #11
    Retired Defense Industry Engineer jadnashua's Avatar
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    FWIW, you can connect a water softener so that it only conditions water going to the heater. That way, you'd still have the minerals in the cold taps. Because the volume through it would likely be less, you'd use less salt verses conditioning all the water to the house.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member andream's Avatar
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    Thanks for the tip. I'll suggest it to the plumber.

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    DIY Senior Member lifespeed's Avatar
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    We get minerals from our food, minerals in the water are a gnat's eyelash. As you have learned, hard water is damaging to your plumbing and appliances long-term, making a softener a good investment. I like to add an under sink RO filter for drinking water.
    Lifespeed

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    DIY Junior Member bookemdanno's Avatar
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    Why spend the money on a water softener only to not enjoy it's benefits on the cold water as well?

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    DIY Senior Member lifespeed's Avatar
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    Quote Originally Posted by bookemdanno View Post
    Why spend the money on a water softener only to not enjoy it's benefits on the cold water as well?
    ^^ +1

    Softened water is great. If you're going to pay for it, run it through both hot and cold pipes. I like RO for drinking water, feed an undersink unit with softened water also and use the RO model with a permeate pump.
    Lifespeed

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