I'm assembling a series of mini-tutorials on my site intended for people who are starting down the path towards a wood heating system. I have all the appropriate disclaimers, and it's not intended to be a complete how-to for heating system design. Basic format is brief discussion, pros and cons, then what we did and why. I'm doing a section now on circulator vs. zone valve based systems, and I'd like some feedback on the content. In particular, I'd like to make sure I've captured the 'pros' - the advantages of pump based systems. There will be another section that talks about supply/return vs. primary/secondary loops. Here's the content: Circulator based or valve based zone control? There are a near-infinite variety of plumbing approaches, but one useful distinction is pump-based vs. valve-based zone control. In a pump based system, each heating zone has its own circulator pump which runs when there is a demand from that zone. In a valve based system, there is one circulator pump at the boiler and each heating zone has a zone valve which opens when there is demand from that zone. If there's more than one heat source, each source typically has its own circulator. In a pump based system, each zone thermostat goes to a controller which controls the pumps. In a valve based system, each thermostat is wired directly to the corresponding zone valve. Contacts in the zone valves provide a demand signal to the boiler when the valve is open. Circulator pumps and zone valves cost about the same, so there is no significant cost difference. Both are reliable and easily repaired. Pump pros: Pumps can be sized to the flow requirements of each zone. Flow rates can be better controlled. Pump cons: Pumps consume more power than valves. Pumps do not provide positive isolation - water will flow forward through a pump even if it has a chack valve. It can be more difficult to understand what's happening in a system with multiple pumps. Our choice: We went with a valve based system, in part because that's what our plumber had recommended for our initial oil boiler installation. The lower power consumption is also a factor, and our installation is designed so that there is only one active heat source and one pump running at any time. That make it easy to understand what's happening with the system. We are upgrading to a multiple speed pump for the wood boiler to provide better control of flow rates.