Question on Hot Water Heater Recirc. Pump

Discussion in 'Plumbing Forum, Professional & DIY Advice' started by beantech, Aug 11, 2011.

  1. beantech

    beantech New Member

    Messages:
    5
    We recently purchased a 2 year old house that has what I believe to be a recirculation pump near the bottom of the water heater in the garage. It runs into the bottom of the water heater where the drain is located.

    Now if I understand this correctly, this is a recirc. pump that constantly moves a small amount of water through the hot lines so that when hot water is needed at a faucet, the wait isn't as long to get it.

    My issue is that the pump appears to be failing. It stops at various times (not on a timer) and has to be unplugged for a time to "reset" and then it starts working again. The thing I don't understand is that when the pump isn't working and is unplugged, we never get truly HOT water....it gets warm and mildly hot, but not at all close to what it is with the pump running. My theory is that when the pump isn't running, the faucet is actually drawing hot water from both the top and bottom of the heater. Since the colder water in the heater is at the bottom, it creates a "mix" of both really hot and just mildly hot water. Does this make sense?

    Anyway, I'm having the pump replaced tomorrow and wanted to tell the plumber to put an inline shutoff valve on the line right before the pump. This way, if it fails again, I can simply close that valve and the faucets will then pull the hot water ONLY from the top of the water heater. For that matter, we may not even mind the slight wait to get the hot water from the tank and may just leave the pump disabled with that valve closed?

    I hope I explained that correctly, and appreciate any comments and suggestions you may have.

    Thanks,
    Mark in FL
  2. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,157
    Location:
    NW Ontario, Canada
    A checkvalve would achieve the same result without fear of closing it while the pump is on and burning out the pump. There exist other brands/models of pumps with timers on them so that you don't need to run it 24/7.
  3. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,386
    Location:
    Yakima WA
    The line that is goes from the pump to the water heater is the return line. The hot water comes out the top and goes to the various fixtures. The return line attaches to the hot water line at a point farthest away from the water heater. There are other important parts to the system and a valve should be one of them. I have a recirculation system and the pump is not on a timer so it runs 24/7. Been like that for about 8 years with no problem. I get hot water virtually instantly from all of my hot water faucets. Your plumber should be able to determine if your system is connected correctly and if all of the necessary components are present and functioning.
  4. beantech

    beantech New Member

    Messages:
    5
    Thanks for the replies.
    Did my explanation of the water temp. when the pump is disabled make sense?
  5. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,157
    Location:
    NW Ontario, Canada
    Yes, it is very plausible that flow is reversing, providing some water from the bottom of the heater.
  6. beantech

    beantech New Member

    Messages:
    5
    Thanks...

    The line that feeds the pump comes from the house. I don't see any valve installed on it.
    Where would a check valve be on this type of system and what purpose does it serve?

    Also, our pipes are cpvc. Is there increased wear on the pipes using this type of continously running system?
  7. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,157
    Location:
    NW Ontario, Canada
    The best place for a checkvalve would be between the discharge side of the pump and the tank. The purpose would be the same as the hard valve you want to install.
  8. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,386
    Location:
    Yakima WA
    I don't know what brand pump/system you have, but the Laing system that I installed has very explicit and detailed directions on installation. You might try a Google search on your brand and model to see if you can find any installation directions. These are great systems when functioning correctly, so this would be the time to get yours fixed right.
  9. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,048
    Location:
    Cave Creek, Arizona
    The check valve, if there is one, is broken. The new installation should have a new check valve, and at least a shut off valve between the pump and tank. THAT valve should be adjusted so it ONLY circulates the amount of water needed to keep the line hot. ANYTHING more than that can cause erosion at piping turns and cause leaks.
  10. Winslow

    Winslow Plumber

    Messages:
    450
    Location:
    Hawaii
    the recirculating line shouldn't be plumbed into the bottom of the heater, it should be plumbed to the inlet ( cold side)of the heater. Coming from the furthest fixture it should have a ball valve, the recirculating pump and a check valve (prefferably a spring check) in that order, then tee into the inlet side of the heater. The original installer probrably thought it wouldn't matter because the cold side has a dip tube but you never know what can happen when it isn't done correctly.
  11. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    27,048
    Location:
    Cave Creek, Arizona
    Windslow, recirculation lines have been connected to the bottom of the heater for over a century. Connecting to the inlet to the heater is a relatively new concept, which was adopted to make an easier connection. The tee BEFORE the pump is optional to make servicing easier, but one AFTER the pump, (and before the heater), is ESSENTIAL for flow control purposes. Trying to modulate the flow with a valve before the pump will induce cavitation and damage the pump. The dip tube is the ONLY reason connecting to the cold inlet will allow the circulator to work properly.
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