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tempering tank

I would like to install a tempering tank to increase the first hour rating on my water heater.

I was thinking about using 2 4" dia PVC piping lengths. If I raise the water temp coming in building from 50 to 70 deg. F, then I just have to heat the water from that point to 125 deg.

My questions are can I use PVC with potable water?

Up to what pressure could i use PVC to?

Does anyone have any experience with this?

Will it work?


  • mark schofield
    mark schofield Member Posts: 153
    electric water heater

    possibly go to Lowes or Home Depot and get a small entry level electric water heater (30 gallons), don't electrify it,  and feed the water heater with that. No need to make pvc adaptors and worry about preasurization.
  • CMadatMe
    CMadatMe Member Posts: 3,086
    Let's Say

    You have 100,000 btu/hr sitting there.

    100,00/ (75 x 500) = 2.67gpm

    100,00 /(55 x 500) = 3.64gpm

    Is that labor worth a gallon per minute? In the end you would be better off increasing set point to 140 in the tank, adding a mixing valve and mix down.

    There was an error rendering this rich post.

  • SWEI
    SWEI Member Posts: 7,356

    You're wanting to use ambient air temperature to bring up the water temp?

    Most codes prohibit the use of PVC for potable water inside the building envelope.  It won't conduct heat all that well anyway.  The electric water heater would sort of work if you removed all its insulation, but you might have external condensation issues.

    You want maximum surface area plus some airflow.  I'd probably look for a large used fan coil and duct the fan someplace I needed cool air.
  • hot_rod
    hot_rod Member Posts: 22,261
    a copper drain tube

    pre-heat is worth a look. Or go to a plumbing supply and buy a galvanized water (well) tank. Around here under 200 bucks, for a 60 gallon. Leave it un -insulated to pick up ambient temperature. remember it may sweat in the summer :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Hump Head
    Hump Head Member Posts: 4
    Tempering tank

    Ok a Galvanized tank , I didn't think of that.
  • heatpro02920
    heatpro02920 Member Posts: 991
    What is the original problem

    and how severe, it would be terrible to spend $400 getting yourself an extra gpm when you really need 3 gpms and you are adding another component to fail in a few years.... I would say if you need more DHW there are most likely a dozen better ways to get it than what you are thinking... Tempering, more storage, higher temps, new system, ect..
  • Hump Head
    Hump Head Member Posts: 4
    edited May 2013
    Ok going

    I don't want to spend a whole lot of money. This is my house not customers .

    This was just some I was kicking around a couple of years. I would also like to remove the sediment before it went to my water heater

    I'm also thinking my bill would go down
  • Henry
    Henry Member Posts: 998
    Pre heat

    Any pre heat tank or piping risk legionella and an assortment of bacteria if your HWT is not at 140F. The energy savings for a residential unit is minimal while the risks are very high of personal injury! The installation costs do not justify any energy savings as this has been tested for many years!
  • heatpro02920
    heatpro02920 Member Posts: 991

    I take it this is well water? If sediment is the issue, how about a filter?

    You can install a rusco spin down filter {larger one, not sure of the number} say 100 micron, then a 4.5x20" housing with a 15 micron filter and another 4x20" with a final stage -5micron cartridge, that will let you store about 5 gallons of water out of the ground in your ambient conditions, and stop any sediment issues... I have a rusco spin down with 2- 4.5x10" filters before my water filtration system and in the summer when the water sits in there for a long time the gauges show its not as cold as the incoming water, so Im sure it would help your cause.... Them filter housings can be had for around $40 each and the rusco is around $65, the filters themselves vary depend on what you want...
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