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Thread: Very hard water and tankless?

  1. #1
    DIY Member Dorrough's Avatar
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    Question Very hard water and tankless?

    He wants to install a tankless propane water heater. We have a well, and it's cave water. I mean, it tested at about 100 grains of hardness after we put the well in. Is this going to cause problems with a tankless heater? Do we have to run it through the softener first? It seems that the water is so hard, that it will be salty going into the heater.

    I don't like the idea of tankless after reading all these threads, and I'm even more concerned about the hardness of the water ..

    Thanks for any advice.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Several things against this choice...pressure changes are fairly normal with a well, and these may make problems with the tankless. If you softened it first, mineral deposits should not be an issue, but you'd still have to maintain it more than a tank type. You'd want to soften it regardless of the WH type you choose, as mineral deposits would affect not only the WH, but faucets, sinks, and tubs as well.
    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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    Master Plumber master plumber mark's Avatar
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    Talking Cave water....not good with tankless.....

    Cave water.....
    or do you mean water from the bowells of hell???


    water from cave very bad for tankless coil...

    probably will need to be de-limed every other month and

    will need constant maintaince. to keep it de-limed.....

    in a few years you will regret going for a tankless
    propane watre heater...

    it would be wiser to put in a simple cheap tank type heater


    but I know that you or someone else in your family
    is hell bent on going green,

    and you wont heed my dire warnings...

    take that leap of blind faith and dont look back


    good luck....

  4. #4

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    Tankless water heaters are pre set around 120 degrees and scaling usually begins above 120. A tankless holds no water. In traditional water tanks the temperature is set at 140 degrees (required in many states) and scaling builds up on the stationary coils. So with a tankless unit it is not really a major issue. Buy a set of webstone isolator valves so you can flush the heat exchanger every 6 months to a year with a vinegar solution (if it needs it).

    Hope this helps

  5. #5
    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by Rockwater View Post
    Tankless water heaters are pre set around 120 degrees and scaling usually begins above 120. A tankless holds no water. In traditional water tanks the temperature is set at 140 degrees (required in many states) and scaling builds up on the stationary coils. So with a tankless unit it is not really a major issue. Buy a set of webstone isolator valves so you can flush the heat exchanger every 6 months to a year with a vinegar solution (if it needs it).

    Hope this helps
    Gotta love a one poster solving the issues that resident plumbers with experience have been fighting.

    Do you work for Webstone??
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  6. #6
    In the trades Dana's Avatar
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    No matter what, run all incoming water through a water softener- that sounds NASTY!

    If green's your goal (either carbon or cash-savings), in FL between state rebates and federal tax incentives (as well as some local city & utility subsidy) solar hot water with electric-element for backup can often be had for similar money to a whole-house propane tankless install. (It just doesn't take all that much solar collector to work in FL, and it doesn't need to be an overly complex freeze-protected system since freezing weather is typically brief and none-too-deep.)See:

    http://www.dsireusa.org/incentives/i...id=1&ee=1&re=1

    If endless hot water is your goal, solar doesn't cut it any more than any other tank though.

    But for long showers (and NOT tub-filling) the capacity can be effectively doubled with a shower-drain heat-recovery heat exchanger like a GFX or Power-Pipe (for about $500-700, works with any hot water heater.) see:

    http://www.renewability.com/uploads/...e_retrofit.pdf

    http://www.renewability.com/

    http://www.gfxtechnology.com/VGFX.html

    It may take a decade to pay for itself on utility bills if your rates are cheap, (but it surely will in marital-counseling costs after numerous cold-showers avoided. :-) ) In more expensive water heating situations (like running an electric tank heater @ 20cents/kwh in cold-water MA) the payback is within a very few years.

    Since it's a counter-flow heat exchanger the water flow has to happen at the same time as the drain flow to get anything like full benefit, which is why putting it on the drain from the main shower is key. If there isn't enough headroom for a tall one (as is the case in many FL homes), short fat ones can work as well- it's the total surface area that's key to performance. (A 48" 4-incher works about the same as a 60" 3-incher, etc.)

    In a few cold-water states they're offering rebates on 'em for the energy savings (WI kicks back $400 on these for electric-tank users!) but energy-savings aside they can be worthwhile in houses where you don't have the space for an 80-100 gallon tank and you have 3-4 people who want to take showers in succession.

    In combination with solar it boosts your solar fraction, with gas/electric tanks it doubles the continuous/successive shower time, with a tankless it gives you higher effective-flow (you can run the laundry & dishwasher without freezing the person in the shower, since the shower is using only half as much hot-flow and it's incoming water temp is higher) In warm-water FL it turns a typical 30-35kbtu/h propane or gas tank HW heater into a continuous flow shower heater, pretty much as-good-as a tankless for that purpose. There are plenty of situations where the expense can be rationalized completely independently of energy costs, if showers are a big fraction of the hot water used. (Showers typically account for ~40% of hot water use in 3-4 person households.)

    But if you live in a slab on grade with the shower on the first floor retrofitting one might be tough, eh? ;-)

  7. #7

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    Quote Originally Posted by FloridaOrange View Post
    Gotta love a one poster solving the issues that resident plumbers with experience have been fighting.

    Do you work for Webstone??
    It is well established general info - you can find it anywhere. This quote from water treatment information... "As the water temperature increases, the more mineral deposits will appear in your dishwasher, water tank and pipes. By reducing the heat of your boiler to about 55C (130 degrees), you will have enough hot water for your shower and you will reduce the amount of mineral build-up in your pipes and tanks. Use rinse agents to remove mineral deposits There are many rinse agents available to remove mineral deposits from crockery and dishwasher. Alternatively, you can use white vinegar by using the dishwasher dispenser or placing a cup of vinegar on the dishwasher rack. Boil some white vinegar in your kettle as a useful way of removing hard water deposits."

  8. #8
    In the trades Dana's Avatar
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    Quote Originally Posted by Rockwater View Post
    It is well established general info - you can find it anywhere. This quote from water treatment information... "As the water temperature increases, the more mineral deposits will appear in your dishwasher, water tank and pipes. By reducing the heat of your boiler to about 55C (130 degrees), you will have enough hot water for your shower and you will reduce the amount of mineral build-up in your pipes and tanks. Use rinse agents to remove mineral deposits There are many rinse agents available to remove mineral deposits from crockery and dishwasher. Alternatively, you can use white vinegar by using the dishwasher dispenser or placing a cup of vinegar on the dishwasher rack. Boil some white vinegar in your kettle as a useful way of removing hard water deposits."

    Scale can form at 50F if the water is hard enough- don't kid yourself that going from 140F to 130F or 120F is any sort of magic bullet or dramatic difference. But higher temps does precipitate more calcium.

    And standby at higher temps makes for higher total scale formation.

    But a tankless heater is just a tiny water-tube boiler, susceptible to water-tube boiler issues. In high-hardness conditions it'll scale up and eventually plug without de-liming maintenance, whether it's set to 120F or 180F output.

    OTOH, going into it with that knowledge ahead of time. plumbing in a few extra valves for a semi-annual vinegar rinse makes can make the maintenance dead-easy. For users who are good about maintenance schedules, (they check the oil on their car at least once every 10,000 miles :-) ) putting de-liming on the same schedule as changing furnace air filters or something keeps problems from cropping up. For the "out of sight out of mind" folks it'll go until it's plugged up and nearly destroyed no matter how easy you make it for them. Know your audience.

  9. #9
    DIY Senior Member lifespeed's Avatar
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    Default too hard for any heater

    Water that hard will ruin lots of things in your house, not just a tankless water heater. A tank heater will be destroyed also, just more slowly. If you don't already have one, you should get a water softener as well as a water test to determine if you have iron or manganese to remove.

    Bad water will wreck your dishwasher, faucets, scale up your pipes and the list goes on. Once you have addressed the water quality issue you can use either a tankless or tank type of water heater. You will also want a Reverse Osmosis filter for drinking water, as the treated water will be high in sodium. Yes, it is not cheap, but neither is periodic replacement of your water-using appliances and plumbing.
    Lifespeed

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