Hi,

I have a hydronic heating system at home with a boiler circulating hot water under my floors. Recently my plumber suggested that I only half-open the water intake valve to my hydronic boiler because fully opening the valve can sometimes cause dripping.

At first I was concerned that this might decrease the water pressure of my whole heating system, but after some online research it seems this wouldn't be the case. Nevertheless, I would like someone to confirm that my understanding is correct:

My understanding is that half-opening the intake valve would only reduce the "FLOW" when the water is moving through the valve. (For example, if I drained my system and started refilling, if would take more time to refill the system with the intake valve only half-opened)

However, when the system is properly filled and not requiring any water intake, the "STATIC PRESSURE" within the whole system would remain the same whether the valve is half or fully opened, and it is this static pressure that's measured by my pressure gauge.

In other words, half-opening the water intake valve will only slow down the process of refilling (or re-pressurizing) an under-pressured system, but once that process is done it will NOT cause the overall water pressure of the system to drop.

Is my understanding correct? Please advise.

P.S. I am assuming my pressure regulator is functioning properly. I also know the water in my hydronic system is not truly static because it is being moved by a circulator pump, but for the sake of simplicity I am assuming that the pump has no effect on the static pressure reading (i.e. the system water pressure gauge). And again for the sake of simplicity, I am also ignoring the pressure fluctuation between heating cycles.

alex, you are at least 8 or 9 times smarter than your plumber..(maybe more)
once the pressure reducing valve for your heating system is satisfied that the system has reached the pre-set pressure, it closes and you could have a 4 inch pipe with a wide open ball valve feeding the system and nothing will happen.
if the pressure reducing valve is not functioning correctly, you could be feeding the system with a 1/4 inch pipe with a ball valve 1/8 open and the pressure will still enter the heat until the relief valve blows.

That's right.....And if you radiant floor heating is below your auto-fill valve, you only need a couple pounds of pressure on the gauge(cold).

Thank you for the compliment! @Packy

So as long as my pressure regulator (or pressure reducer in this case) is working properly, pressure wise it doesn’t matter how big or small the water intake opening is, correct?

That's correct......the pressure would equalize, whether it was a pinhole or a wide open valve.

If your "expert" said that, then you need a better "expert". Partially closing a valve only reduces volume and DYNAMIC pressure while water is flowing through it.

Well said!