Proper Gas Hot Water Tank Flushing

Discussion in 'Water Heater Forum, Tanks' started by John28, Jul 18, 2015.

  1. John28

    John28 Member

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    My unit is a year old now, which I'm going to drain and flush. First I'll turn the thermostat off and shut the gas line off to drain. But my question is, how long should I wait for cool down for the tank to normalize before filling or flushing with cold water?

    I read where many set it to pilot drain and and refill, which doesn't seem like a good idea to me, I think you'd want the tank to normalize before flushing or filling with cold water, and not have a constant pilot on it? Thanks
     
  2. DonL

    DonL Jack of all trades Master of one

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    Putting it on pilot is fine. Is it popping when it heats ?

    Good Luck. You may want to have a new drain valve on hand.
     
    Last edited: Jul 18, 2015
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  4. John28

    John28 Member

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    Nothing wrong with unit, just doing a yearly maintenance drain and flush. I don't want to induce cold water to a hot empty tank, and was curious of how long for cool down, 5min., 1/2 hour, 2 hrs? And I know a pilot is not much heat, but is it even a good idea to leave a pilot on an empty tank? And refilling with cold water, the tank will never cool completly before fill ing?
     
  5. DonL

    DonL Jack of all trades Master of one

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    You do not have to drain the tank completely. Normally opening the valve and watching for clean water is good.

    I would think 1/2 drain would be good, with a new drain valve in hand.

    If it is not making strange noises, it may be best left alone. You start messing, they can start leaking.


    Good Luck.
     
    Last edited: Jul 18, 2015
  6. John28

    John28 Member

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    Not sure you are following? No the unit is not popping, its new, 1 year old.

    My manual says to drain once a year as preventative maintenance. You stated if its popping, go ahead and drain, otherwise don't. Which totally makes no sense? Isn't the purpose of yearly draining to keep it free of sediment so it don't start popping in the years to come?
     
  7. DonL

    DonL Jack of all trades Master of one

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    You should follow the manual.

    Is your drain valve plastic ?
     
  8. Reach4

    Reach4 Well-Known Member

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    If your gas water has a standing pilot, I would turn the control to the Vacation setting. That will keep the pilot on but turn off the burner. Then I would drain without worrying about cooling things first.

    If you want to drain and flush, I would turn off the water to the water heater and drain all the way. Then I would try to stir up any debris and let that drain out. Then repeat until you are not getting fresh debris.
    1. One way to stir things up is to quickly turn the water on for several seconds, and let that drain. Water comes in thru the dip tube. That will play water onto the bottom, and will shake up some debris. https://terrylove.com/forums/index.php?threads/water-heater-question.59350/#post-439615
    2. Another way is to spray water into the anode hole after having removed the anode temporarily. That has the advantage of not having a fixed aiming point.
    3. If you have replaced your drain faucet with a full port ball valve assembly, you could stick a wand/rinser into the hole and spray around the bottom fairly closely. There is a water heater rinser sold for RV water heater cleaning, and I think somebody could use one of those. Something longer would be better. I have wondered about using a wand from a small electric pressure washer. https://terrylove.com/forums/index....rain-valve-with-ball-valve.55265/#post-426951
    4. I have read of connecting some tubing onto a vacuum cleaner hose and trying to suck up particles while the tank is drained. This could be via the threaded hole while the drain was temporarily removed.
    If you just use #1, you will be way ahead of the great majority of people. That is easiest, and it will do fairly well. I did #1 and #2.
     
    Last edited: Jul 19, 2015
  9. DonL

    DonL Jack of all trades Master of one

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    Very nice Reach4.

    I have good water and a whole house filter here, and really do not go with all of the "Manufacture Suggestions" just to get another year out of a appliance. Plus the chance of fixing it until it is broke. They love it when you break it.


    Cleaning the burner is higher on my list of things to do on a gas heater.
     
  10. John28

    John28 Member

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    I'm not concerned the least bit about draing the unit hot. My only concern is refilling a hot unit, which tells me no piot at all and let the tank normalize before filling or flushing with cold water. This don't make sense?

    And yes the drain valve is plastic on my Rheem tank. Do these plastic drains fail due to very hot water going through them? Where one might even want to let the tank stand idle for a good while so you are only draing luke warm water through it, vs. very hot water?
     
  11. Reach4

    Reach4 Well-Known Member

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    I would not worry about adding water to a tank that was switched to vacation mode and then drained or was empty but in vacation mode for a few hours. I am not a pro. But I don't see the thermal shock being that bad. If you want to turn off the gas and let things cool before adding water, that would be fine. I did not do so. Extra caution would not hurt the process.

    I don't think a domestic water heater can make very hot water. I think the water heater can probably only make 160 max. I wouldn't worry about your plastic drain taking the heat during your flushing process. IMO the reason to maybe switch to metal is to provide a more open path to get better flow and therefore carry debris out better.

    What I would not do is to have the control set above vacation mode without the water heater full of water.

    I suggest letting your drain water flow into a pan where you can see the debris, and maybe post a picture for our education and curiosity. My debris was impressive.
     
    Last edited: Jul 19, 2015
  12. DonL

    DonL Jack of all trades Master of one

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    If you are going to do this once a year I would replace the Valve with a brass one.

    At least have one on hand for when the plastic one breaks.

    I am sure Hot water does affect them, and is one reason they get brittle and break. Good luck getting it out of the tank easily then.


    It is best to collect what comes out for close examination. Take a PH measurement.
     
  13. Master Plumber Mark

    Master Plumber Mark Sensitivity trainer and plumber of mens souls

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    You guys are all nuts.. take a ph test on your water...??? What for

    You cannot drain a heater and expect the sediment to simply come out on it own.. it will just lay in the bottom of the tank... you need to blast it out under pressure

    If you want to do this every year, just put a garden hose on the nozzle of the heater and simply turn it on full blast...
    YES,,, with FULL PRESSURE out the hose....and let it blast out onto the driveway or into the sump pump pit for a few minutes.. Turn the faucet on and off a few times to stir up the sediment in the bottom of the tank and if there is anything in the tank it will surely blow out under pressure.....

    Leave the burner on and dont touch anything when you do this.. if you fool with the unit you might actually not get it to come back on... Just let the burner kick on and it wont hurt a thing...

    Nothing worth mentioning will dribble out the faucet if it has no pressure to push it out..... you will simply piss out the whole tank and the sediment will just settle and lay in the bottom.......

    you will accomplish nothing but will feel good about yourself draining down the whole heater....

     
    Last edited: Jul 26, 2015
  14. Reach4

    Reach4 Well-Known Member

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    After initially draining and opening the anode hole, I used a small utility pump and float switch attached to a PVC pipe, in a small plastic bin, to recirculate water and catch the big stuff. I also wanted to minimize the water to the septic. Initially I pumped the water from the bin through a hose upstairs and out a window. The recirculating came later where I had a big filter in line with the recirculating water. I forget the whole order of what I did, but it did included draining, and then turning on the feed to produce turbulence and flow. I repeated that many times.

    I think the dark color was sulfur of some form that had settled at the bottom from before I got my iron+sulfur filter. There was more dark water that was not still around when I took the picture that has water. I don't remember why the plastic bag with a bit of 3/4 inch electrical tape was in the bin with the rocks.
     

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    Last edited: Jul 26, 2015
  15. Caduceus

    Caduceus Master Plumber

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    Yeah, just do as Mark stated. Just be careful with the hot water coming out initially so that nobody gets scalded.
     
  16. Caduceus

    Caduceus Master Plumber

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    I have to add that you SHOULD NOT drain a water heater and allow it to cool with the drain valve closed. If the sealed hot/warm tank cools without any vacuum relief (open drain valve or open faucet-hot side) the tank can become damaged from a vacuum. Just do as Mark instructed.
     
  17. DonL

    DonL Jack of all trades Master of one

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    I think PM is good, but some is not needed.

    Better water quality would be my goal.

    The only reason I mentioned PH was to test for lime buildup in the tank. That would be the only reason to drain it.
    Acid is the only way to get all of it out, that I know of. The scale is sure not to come out of the drain valve.
    If it does your drain hose gets plugged.


    How do the new self cleaning ones work ?
     
    Last edited: Jul 28, 2015
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