Our house had always had some latent heat coming through the vents even when they were turned off, which was causing the temperature to be pretty unbearable during the summer. One day, we heard something making a ton of noise in our garage, and we found the source was apparently a circulator pump, which we unplugged. After we did this, the heat from the vents disappeared, and it's been much cooler inside. However, the hot water no longer works with the pump off. Our landlord said he would replace the old pump, but we don't want the heat to come back. So my question:

Why is the circulator pump affecting the heating? From what I've read, it should just be pulling water out of the pipes, it's not clear to me why that would keep the heater hot all the time, even if it's heated by hot water.

Also, is there any way to have the circulator pump running but not heat the house at the same time? It sounds like the pump should save a lot of water, but we don't want to save water at the expense of the extra energy it's consuming and the heat it's putting out.

  • The pump system I had and have installed have been on timers and only ran intermittently to keep the water in the pipe warm/ hot. They did not have to be running or powered to allow hot water to flow. It sounds like it was not properly installed. In this case the amount of waste heat is probably costing much more than the few gallons of water the recirculating system saves, plus the added heat making it uncomfortable.
    – Ed Beal
    Aug 19, 2019 at 16:03

2 Answers 2


High probably you have non-insulated pipes or components in the area of the vent system.

If you do not want completely and professionally remounting the hot water pipe, you have various ways to reduce the heating of the air:

  • Insulate the hot water pipe as much as possible. There are suitable foamed insulations that can be easily pushed over pipes. But you have also to find suitable places in the ventilation duct for inserting.
  • What is the temperature of the hot water? You can set the temperature of the water to 55°C/131°F. Or lower if the system has automatic intermediate heating to combat of legionella.
  • Put a electric timer to the circulation pump. If you do not need hot water all day, you can limit the duration of the hot water pipes.
  • Hello, and welcome to Home Improvement. Thanks for the answer; keep 'em coming. And, you should probably take our tour so you'll know how best to contribute here. Jan 1, 2020 at 11:55

Most likely what happened is that the hot water pipes were run in the same chase (interior wall space) as your heating ducts or even inside of the ducts themselves. That happens when someone adds a recirculating pump system to a house not built that way, because they need to run pipes back to the pump, but it's difficult to get access to chases to do so. So they actually run the return pipes through the existing air ducts or right next to them inside of the walls. Now the heat radiating off of your pipes is getting absorbed and distributed by your ventilation ducts into the rest of the house. Poor design.

What you could do for that is to insulate your pipes, which is pretty much standard for recirc. systems but because yours may have been a DIY retrofit by someone who didn't know that (or couldn't afford it), the pipes are uninsulated. But that assumes you have access to the pipes in the ducts, which may be problematic.

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