Upgrading to a heat pump water heater can lower the cost of making hot water, so a mysterious stream of warm water heading straight to a basement drain immediately raised red flags for one homeowner, who reached out to Reddit's r/AskAPlumber forum for advice. 

Here's what to know

According to the homeowner, the puzzling part was that the warm water was coming from a "small line" feeding into the same drain used by the heat pump condensate line. 

In this case, the flow appeared only while their wife was showering, and they discovered it only after living in the house for almost 10 years. 

"Any speculation on why this would happen?" the homeowner asked, adding that "our power bills have recently been higher than normal which is now making sense."

More background

Some weren't convinced the homeowner showed evidence of a bigger problem. 

One commenter thought the drain line was there on purpose and wouldn't have a major impact on electric bills, writing: "It's intended to keep the P trap in the basement floor drain full of water. It's usually tied into the shower head of the main bath."

"It's a very common thing," another said. 

Others pushed back on that explanation, though. 

"I started plumbing in 1985," a commenter wrote. "I have never seen a trap primer attached to a shower valve." This reaffirmed the homeowner's suspicion that something was wrong. 

"This was like a full tap running," they noted. 

"It's not supposed to be delivering that much water. The quantity is the problem, not the principle," another commenter explained. 

What can be done?

Instead of assuming the root cause of the flow, the homeowner said they planned to try other hot water fixtures upstairs and see whether they produced the same warm discharge. 

The replies also suggested checking the pressure-relief valve on the water heater. Another wondered whether a water softener flush might have happened at the same time as the shower, which would mean the two events were unrelated.

For homeowners who decide it may be time for an equipment upgrade, Cala makes smart heat pump water heaters. Cala's customizable smart heat pump water heaters can help homeowners decrease their energy bills by heating water exactly when it is needed. 

For a household already worried about an electric bill, that kind of timing control could be especially appealing, and Cala is built around that approach.

Where can I learn more?

If rising water or power bills have you wondering where your hot water is going, these stories dig into similar plumbing and cost concerns. They cover hidden leaks, drain habits, wastewater heat, and simple ways homeowners try to avoid bigger plumbing expenses.

• A realtor showed homeowners how blue dye can expose hidden toilet leaks behind rising bills.

• A plumber said hot water helps keep kitchen drains clearer before clogs turn costly.

• In Vancouver, Canada, officials found heat in the sewerage system to help warm homes.

• A plumber shared simple drain hacks that helped homeowners avoid expensive sink backups.

• A homeowner tried a plumber-approved hack to clear a clogged drain without a service call.

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