Sediment in hot water lines with tankless heater

Discussion in 'Tankless Water Heater Forum' started by ryguy, Dec 10, 2009.

  1. Tbone999

    Tbone999 New Member

    Joined:
    Mar 24, 2017
    Location:
    of what
    i have this problem too. I recently re plumbed my entire house supply lines and upgraded the water heater to a tankless heater. The tankless water heater is heating up whatever impurities i have in my supply lines causing the impurities to bond together, that would have otherwise settled at the bottom of my old tank. Now they instead, continue along my supply lines to the aerator filters at each supply faucet. i put a 5 micron and 25 micron sediment filter on my cold main line before it gets to my heater but it did nothing. Next i will try a hot water filter and put it right after my heater and see if it works. if it works it will likely fill up quickly and require filter replacement often. My old rental house had a tankless and we never had problems but we also had a water softener, that could have made the difference. i'll update.
     
  2. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    How hard is your water? Some tankless manufacturers void the warranty if you feed the heater with water that is too hard. In one case, 7 grains is max. There may be others with different rules.

    If you have a well, you should get a lab water test. I like kit 90 from http://www.karlabs.com/watertestkit/
     
  3. Chrisring0

    Chrisring0 New Member

    Joined:
    Dec 5, 2017
    Location:
    Pennsylvania
    I have the same problem it's an electric eco smart 18kw tankless water heater my hot water lines only have crushed shell like materials clogging them cold water lines are clear we have very soft water

    Remodeled the home all new water lines through out

    Is there an option to add a filter after the hot water heater ?
     
  4. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    Yes. Click Inbox. I think you would want a fairly course filter that is not large.
     
    Last edited: Dec 5, 2017
  5. lifespeed

    lifespeed Member

    Joined:
    Apr 27, 2007
    Location:
    California
    You may be seeking to address the symptom rather than the problem. While necessity may dictate you do something to keep the junk out of your water lines at the source, at least in the short term, you may want to get to the root of the problem - which could be hard water deposits. Is your water heater precipitating lime scale onto the heat exchanger? Find out (test) your water hardness and quality. If it is less than 7GPG, flush your water heater with vinegar a couple times a year to prevent buildup. If it is worse you'll need a water softener. Also, you may have damaged your water heater heat exchanger beyond repair. I don't know if it is economic to replace it, but flushing typically cannot remove years of thick lime scale.
     
  6. Chrisring0

    Chrisring0 New Member

    Joined:
    Dec 5, 2017
    Location:
    Pennsylvania
    Thanks for the quick replys was hoping for a quick solution at this point the heater is a year old and is honestly the root of the problem there was a gas tank water heater running for 15 years before we bought the house and not a spec of sediment in the lines .... while we renovate its to hold us over until we can run the new gas lines it's just not economical and takes up massive space on the panel thanks for the help
     
  7. lifespeed

    lifespeed Member

    Joined:
    Apr 27, 2007
    Location:
    California
    Tanks still precipitate hard water scale, it just collects in the bottom of the water heater until it causes a different kind of problem. Tankless reveal the problem more quickly. As to the panel space, tankless electric are pretty crazy. But you know that.

    When I put new plumbing in my house the inside of the original pipes looked like an old man's clogged arteries from the scale. I didn't want my new copper to end up that way, so now have a softener and gas tankless for 6 years, sediment and trouble free.
     
  8. OldSalt

    OldSalt New Member

    Joined:
    Feb 3, 2017
    Occupation:
    IT Consultant
    Location:
    Northern Idaho
    I saw this old thread (started in 2009!), while looking for the procedure to reset the LC (lime scale build up) code on my Rinnai tankless water heater (model RUC98I).

    Off topic: Hint, older units simply required you to unplug and wait 60 seconds to reset this code. Newer units have two buttons inside the unit near where the dip switches. They are tiny, and you're supposed to push both for 5 seconds to reset. LOL, I can cover both buttons with my little finger; the only way to reset them was to use one finger on both buttons. Only the troubleshooting (i.e. repairman's guide) shows how to do this, and a couple copies I found on the internet had that information blanked out, with "call Rinnai or your serviceman" added. Apparently, Rinnai doesn't recommend the descaling and reset procedure for homeowners. In any case, what the directions do not say is that you have to have the unit open and plugged in to reset the switches - so FYI.

    Back on topic. My unit started sending calcification throughout my plumbing almost from the first couple of months it was installed. I first discovered the issue when my unit sent a code 63 (internal recirculation pump flow blocked). I checked the thimble sized filter and it was half filled with what I then thought was sediment or sand from the old city water plumbing (new home in an old lake area). After receiving the code and cleaning out the filter about every 10 days, I finally got a whole house sediment filter and thought the problem was solved. Then the shower head started becoming problematic, and I cleaned that out about once a month. Then the check valve separating cold water intake from hot water recirc return jammed due to particle blockage, resulting in cold water back feeding into the hot water line (i.e. delightfully cold showers, just long enough after you jump in to get your hair fully lathered up; that became a real source of ... ah ... domestic unrest).

    I went through about three more months of trying different filters, and complained to the poor guys who made the unit about their "defective product". I finally got fed up, and replaced the water filter with a clear water strainer (50 mesh, 1" water main line). Then I flushed every appliance in my system.

    Once again, I figured that I had finally solved the problem, and we enjoyed delightfully "instant" hot water - for about a week. Then the check valve jammed again. and then the shower head became filled with debris again, and then EVERY fixture started clogging up. That was when I finally figure out that (a) these units require periodic flushing with an acid based product (i.e. white vinegar), and (b) the problem was on my outbound hot water line.

    I purchased a second, smaller 3/4" plexiglass strainer and installed it. Three seconds after activating the hot water pressure, the strainer was full of debris, confirming the problem. I cleaned it out multiple times, and cleaned and flushed the household faucets and figures. I had a pump and hoses on order to flush the system, it arrived today, and I saw my first "LC O" code. (For the Rinnai units, that code beeps continuously, LOUDLY, and obnoxiously, and the hot water ends. Apparently, this can be overridden by toggling the ON/OFF button 5x, and you'll have hot water for another 70 hours. Then the alarm will sound again with an "LC 1", the system can be temporarily reset again, for a number of times until permanent lock out. )

    I flushed the system with vinegar (look it up on Google; there are video's out there fully describing this), reset the code, and we're back into the hot water game.

    The bottom line for me, as far as lesson's learned, is:

    a) Yes, install a 50 mesh strainer just AFTER the point where hot water exits the water heater. Not only will it protect the rest of your plumbing against sediment, but you'll see the sediment in the strainer, giving you a clue that it's time to flush and clean the system. Rinnai comes with a thimble sized filter/wire strainer on it's intake to protect the water heater (which with recirculation, fills with calcification sediment from the water heater itself). The second strainer I added ought to be standard for every tankless system. Sediment builds in a tank system, but it gathers in the bottom, while hot water is drawn from the top. Any tankless system is going to have a sediment problem, regardless of water quality, because there's no tank to "hide" the sediment that every water heater (of any kind) generates.

    b) I intend to flush this system every 4-6 months as preventive maintenance, pumping vinegar through it for about two hours, regardless of what I see in the strainer.

    c) I'm going to have to get a water treatment system in eventually, even though the hard water here (Northern Idaho) doesn't seem as hard as where I came from (So California).

    This is my first tankless hot water heater. My conclusions:
    • It's solid technology. It's terrific when working normally.
    • However, it depends on very clean, soft water.
    • It's far easier to get a cold water block in a tankless system.
    • Tankless systems require far more regular maintenance than tank systems.
    • This works well for me, because I'm already on propane. I have a 500 gallon tank I use hot water, cooking, backup heat (30K BTU fireplace), and the clothes dryer. (I'm plumbed for a backup propane generator, to be added soon.) Primary heating is via heat pump/electric. We turn re-circulation on and off manually (versus scheduling it) when we want hot water, and have hot water at every faucet in under two minutes. Propane cost me about $18 a month last year, almost nothing, and we're on schedule to spend about $45 a month this year using the fireplace to heat whenever outside temps drop below 30F (i.e. heat pump is not efficient below that temp, and electric coil heating kicks in; our electric bill skyrockets 6x higher). The goal is to drop our $350 a month electric bill to about $150 a month, and increase our propane consumption/cost by $30 to $60 a month. Propane + tankless water heat = cheap hot water and cheaper energy overall (i.e. when propane is at $1.50 per gallon or less).
    • I'd never install a tankless water heater just for the "instant hot water" purpose touted by the manufacturers. I'd only install a natural gas or propane, and propane only as an alternative to an electric tank water heater. Regardless of how well the technology works, it's just too much maintenance and trouble for something I've taken to be "automatic" all of my life, i.e. hot water heated in a tank by natural gas. The fact that I have to think about "hot water", makes it a failure. I'd install a water heater tank with natural gas, and add recirculation, if I had natural gas available.
    Long winded post, but I hope it answers a few questions for people considering propane, or trying to solve their "sediment problem" on their tankless hot water system.
     
  9. Reach4

    Reach4 Well-Known Member

    Joined:
    Sep 25, 2013
    Location:
    IL
    That filter could be one of these: http://www.rusco.com/index.php/product1/hot-water-filters

    Water softeners are nice, even when you don't have a tankless WH. This thread makes me think of what might have built up in my WH before the softener was working.
     
  10. lifespeed

    lifespeed Member

    Joined:
    Apr 27, 2007
    Location:
    California
    You have a hard water problem, plain and simple. If you want a tankless and have hard water you have only two choices: install a water softener, or flush with acid as regularly as required, which in your case it sounds like is every couple months. Something stronger than vinegar, food-grade phosphoric acid for example, could be helpful.

    If you don't want to do either of the above you are better off slowly destroying a tank, which at least will keep operating longer and somewhat mask, but certainly not eliminate the problem.

    I have hard water varying between 7 and 30GPG in northern california. My copper plumbing, Noritz NRC1111 tankless water heater and water softener are 6 years old. I have flushed the tankless with vinegar once. I never get "sediment" in any of my faucets, showers or appliances, and I don't have any filters except for the incoming water to the house; a Granulated Activated Carbon (GAC) backwashing tank ahead of the softener. I have a recirculator with the typical two check valves and an expansion tank. It all works perfectly with minimal maintenance. I love the fact that we can do three back-to-back and two simultaneous showers in the morning without concern of running out of hot water.

    Lastly, "instant" hot water has nothing to do with tank or tankless, that is a function of pipe distance to the water heater. Instant hot water is provided by a recirculator. If you put one on a tankless use a proper time and temperature control system that doesn't over-cycle your water heater. I can provide more detail on this if anybody needs it.
     
    Last edited: Dec 7, 2017
  11. Robert Budach

    Robert Budach New Member

    Joined:
    Jun 27, 2019
    Location:
    El Dorado Springs, Missouri 64744
    I have the cure. It is an easy fix. Once installed, you will be amazed on how effective this is and how fast the clogged screens are flushed out.
    Rusco Hot Water Spin Down Filter System - 3/4" FPT
    Part Number: 3/4-200HT-F
    get the finest screen they make.

    Once installed, you will be amazed to see, and you can see, how much crap is generated by your water having direct contact to the heating element. this is extremely effective, Within a week, the slow hot water problem just washed away.
     
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