Solution to Pressure Loss in a Hydronic System

Hydronic systems are generally pressurized relative to atmospheric pressure to ensure that if there is a leak, it is water leaking out, not air leaking in (which could eventually disrupt water flow and potentially damage equipment). Even the smallest of leaks – so-called “pinhole” leaks that leave little to no evidence as the leaking water evaporates quickly – will eventually depressurize the system. In some cases, depressurization alone will cause the system to stop working; if not, inevitable air infiltration will take the system down in time. The best solution is to construct a system that does not leak; however, when an existing system is reused (as is often the case when we’re converting a boiler-fed system to a heat pump), it is often impractical to examine every pipe for leaks. Even if it were possible, the aforementioned pinhole leaks can be nearly impossible to detect. A common solution is to provide automatic make-up water to replace that which has leaked out.

Historically, make-up water has been provided by connecting the potable water system to the hydronic system (in a way that ensures hydronic water cannot flow into and contaminate the potable system). That presents one or two issues that we’d prefer to avoid. The first is that the potable water may have dissolved minerals, which we do not want in our hydronic system . Secondly, if we have an essentially infinite supply of make-up water (from the potable system), imagine if your hydronic system developed a substantial leak while no one was home to discover it for hours or even weeks… ugh!! The solution to both is a small, pressurized tank of water connected to the hydronic system that can be filled (and refilled) with clean water periodically. This is what we recommend and suggest it as an option when we convert your hydronic system from boiler to heat pump. It can save you hundreds of dollars in avoidable service calls to re-pressurize your hydronic system, you can control the quality of the water entering your system, and you limit water damage should a leak suddenly develop.