Higher temperature water heater overflow valve?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Melissa2007B, Jan 30, 2013.

  1. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    We dont have a regulator yet.
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    I do not suggest a retrofit without dedicated return. Those have thermostatic valves that stop the flow once the water at the POU is up to temp. It does not put scalding water into the cold line. It also does nothing to combat stacking. To combat stacking, the recirc needs to be continuous to blend the water in the tank.
  3. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    I'm not sure what you mean then, or how it can be done.

    It was my understanding that a recirc system needs to create a loop of all the hot water line, going all around the house, then a small pump pumps it. But the bottom of the house is covered in insulation and plastic, so I'm not clear how an insulated recirc loop could be done.
  4. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    If the intent of the recirc is to have ready hot water at all the faucets, then yes, what you describe is true. If all you want to do is use a recirc to prevent temperature stacking, then the recirc does not have to go all the way out the the farthest faucet or to any faucet for that matter. It simply needs to draw off a small continuous supply of hot water from the top of the tank and send it back down to the bottom.
  5. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    Yes, I understand that, but I should try using cold water for the humidifier first, eh?

    As far as circulating around the whole house, I'd love to, but the cost...

    But it's real obvious now, that we gotta get that pressure regulator on the input water supply to the whole house!
  6. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    21,814
    Location:
    New England
    You do not understand the retrofit recirculation systems' operation. Plus, as I said, when you add a PRV, you MUST add an expansion tank. THe PRV will only prevent the supply's pressure from rising, it will do NOTHING about the rise from the WH heating the water except possibly make it worse.

    A retrofit system uses a cross-over at at least one sink. It has a thermostatically controlled valve in it. It is usually set to somewhere around 100-105 degrees. WHen the water there reaches that point, it shuts of. On most, the pump keeps running, but the valve is closed. So, the 'cold' water will never get hotter than the setting of that crossover setting. The only one I know of where this is user adjustable is the RedyTemp unit. Now, depending on the layout of the house, that one may not run long enough to combat the full stratification effect.

    But, while that effect is possible, are you SURE that's what's causing the T&P to discharge? Do you get nearly boiling water out of the hot tap? If not, then it's a pressure issue, and the stratification is not severe enough to create your problem, it's all pressure. A closed system without an expansion tank can easily get to high enough pressure to open a T&P safety valve. It happens all the time. You MUST have somewhere for that expanding water to go, and you seem to be ignoring the fact of an expansion tank. Assuming you have a PRV installed, insist they also add an expansion tank - any good plumber would know this, and, it's required if you get a permit and have it inspected.
  7. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    Apparently I don't understand. At Home Depot they were showing me a water pressure regulator that they said could be put before the water enters the house and keep the pressure from ever going too high after it enters the house. Are we talking about the same thing??? They didn't mention any tank.


    What people here have been suggesting is just a loop around the house, and a pump. Then the temp gets set in the water heater where it gets set now, and stays that way.

    NO, and the pressure appears to be causing it. I said the pressure has been between 80-99 PSI just tonight. I'm convinced it's the pressure.

    YES. I agree.

    YES, because the city water pressure is 80-99 PSI coming INTO the house. What good will an expansion tank do??? It needs to be regulated before it enters the house, which is what Home Depot suggested, pending my measuring the PSI, which I just did.

    NOTHING is installed yet, except the PRV on the water heater, but it's being caused by city water pressure, NOT temp.

    Are we on the same channel?

    http://www.homedepot.com/h_d1/N-5yc...pressure regulator&storeId=10051#.UQtHVM_jFyI
    Last edited: Jan 31, 2013
  8. DonL

    DonL Jack of all trades

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    Location:
    Houston, TX
    You can not compress water.

    When water is heated it expands, and requires more room. If no extra room to expand then pressure goes up.

    Is that hard to understand ?

    It is simple really.
  9. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,833
    Location:
    NW Ontario, Canada
    Water does the same thing when it freezes.
  10. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    Yes it certainly does, about 9% expansion
  11. DonL

    DonL Jack of all trades

    Messages:
    3,812
    Location:
    Houston, TX

    How much does water expand in a vacuum ?
  12. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    If you rely on advice from a big box store, you'll have many things in your home that may work most of the time, but will never pass code and won't work at all under some circumstances.

    A PRV is essentially a one-way valve...this makes your house plumbing 'closed'. Any expansion caused by heating isn't going to expand your pipes like a balloon...the pressure rises and something has to give. This is usually the T&P valve on the WH. It could be the washing machine hose ballooning out (not good for it!), or a faucet supply hose, or often, the weak link is the toilet fill valve or a dripping faucet. With a closed system and a large use of hot water (where you're reheating a significant volume of it), the pressure will rise high enough to open a T&P valve UNLESS something is either leaking out the required volume, OR, there's a place for it to go. The goal is to keep the pressure steady at a safe value for plumbing, and not rely on the T&P safety (fault) valve to do it. Nothing in your house likes the water pressure that high. The only way to keep it steady that's approved and doesn't waste water is an expansion tank...

    I worked with programmers for over 25-years...while a generalization, they all seem to think they're always right...code says, you need an expansion tank, regardless of what the guy at HD says! The PRV will regulate the supply, but inside the house, when the water expands, without somewhere for it to go, the pressure WILL rise, and often significantly. Note, many water suppliers install a check valve on your water inlet that does the same thing - makes your house a closed system, and that requires an expansion tank, even if the local water pressure isn't too high as well. If your house doesn't have one, it may when they ever do some maintenance on the supply. Having a closed system makes the whole water supply safer since if for some reason, yours got polluted (you left the hose sitting in a puddle and the dog just shit there), it can't work its way back into the system and create problems. Same reason why a special valve is required on sprinklers, you wouldn't want a hiccup in the supply to draw fertilizer, insecticides, etc., into the water. A hiccup might occur when say the firemen open up a few fire hydrants to fight a fire...the pressure drops, and water from your house gets sucked back out into the system, or they shut things down for maintenance, instead of having to drain hundreds or thousands of houses, the water stops sooner since what's in your house, can't get back to the supply.

    You still don't understand how a retrofit recirculation system works...there's a thermostatically controlled crossover valve in the system between (normally) the furthest fixture's hot and cold. When the hot water is below the thermostat's setting (at the crossover, not in the WH), the valve opens, and pushes water back into the cold water supply line. Once the water at that valve reaches its setting (often 100-105 degrees or so), the valve closes. So, and since it may not have to push that hotter water all the way back through the supply system to achieve the desired temp in the hot line, the cold water line would never get above the thermostat's setting in the crossover.

    The system I have is a self-contained box and has the pump, crossover, and thermostatically controlled valve all in one neat package (RedyTemp). It is the only one I know of where you can adjust the aquastat's value. I have mine set to just make the water warm at the sink (near body temp). The shower supply takeoff is closer to the WH, so it's hot almost immediately. At the sink, it gets hot quickly, since it's already warm. If I flush the toilet, by the time I get to wash my hands, the cold is actually cold since it has flushed out enough warm on the cold side. Everywhere else in the house, the cold is cold because I stop it earlier than with most of the other retrofit recirculation systems, and this approaches the convenience of a dedicated return line (not easily done in many places on retrofit).
    Last edited: Feb 1, 2013
  13. BobL43

    BobL43 DIY Senior Member

    Messages:
    1,786
    Location:
    Long Island, NY
    It will change to yet another state, like moving from NY to Texas:p English is a fun language
  14. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    This is all confusing me, as I'm not a plumber. I understood that we can put a regulator where the water comes in from the street line into the house, and it will keep the pressure after that, inside the house, from ever going over 70 PSI. Correct?

    All this other stuff just confuses me.
  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    If you didn't have a water heater, yes, it would limit the water pressure in the house. BUT, you DO. Heating that water expands it. That will increase the water pressure since it has no place to go. Get an expansion tank installed when you put in the PRV, and that gives the heated water someplace to go so that it doesn't raise the water pressure.
  16. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    Oh ok, I see what you mean now. BUT, the problem seems to be heating the water at 90 PSI instead of at 70 PSI, so it's opening the TP valve on the water heater. I was thinking that by regulating the whole house's pressure at 70 PSI, it might be fine, right?
  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    The higher the incoming static pressure is to start with, the closer it is to the point where the T&P valve will open. It takes very little volume increase to create vast amounts of pressure in a closed system. Lowering the incoming pressure will help the health of ALL of your plumbing fixtures. But, it will still expand and increase over the incoming supply if there's no place for the expanded water to go. Just put in an expansion tank with the PRV, and it should solve your problem. Note that a T&P valve is designed to be tested once a year; not operate daily. It is a safety, emergency relief valve to protect the WH from literally blowing up and taking your house with it. If yours has been operated a lot, it's a good idea to replace it when you put in the PRV and expansion tank. Then, all things being right with the world, it should only open during an emergency, fault condition, or you manually open it to test that it's still capable of opening during your annual check.
  18. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    By PRV you mean the one on the water heater? What do these expansion tanks cost? Easy for me to install myself?

    Seriously? Blow up THAT bad?

    Hmm, OK. I just replaced the valve on the water heater, maybe 18 months ago, and now it's dripping. Tired of this...
  19. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,814
    Location:
    New England
    The T&P valve and a PRV are two different, separate, items. A PRV goes on the house's inlet water and is what adjusts the street pressure to the desired pressure in the house (most people recommend somewhere around 50psi - the new gauge you bought will help you to adjust this, should you need to on a new valve). Then, the expansion tank goes somewhere after the PRV, but before the cold inlet to the WH. Because the T&P is not designed to open and drain regularly (only in an emergency situation or fault), when it has been draining regularly, it's not a bad idea to replace it. The PRV keeps the street pressure from coming in too high; the expansion tank keeps it from rising because the heated water is bigger in volume.

    Yes, a bad or non-existent T&P and a runaway WH can literally blow a house down. Do a computer search, and you'll find pictures of some that have happened in the past...you don't want to mess with one of those, and you really want one that is working properly.

    If a WH keeps heating and there's no place for the water to be relieved, water expands over 500x its size when it makes steam...think about it, when it blows the seam because it isn't working, it almost instantly becomes over 500x bigger. It's not pretty. Luckily, the safety features usually work, and they don't fail often.
  20. Melissa2007B

    Melissa2007B New Member

    Messages:
    102
    Location:
    Denver, CO
    Last edited: Feb 1, 2013
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