Stop getting sicker
Air Purge Index
The concept of purging is to force air
from one end of a series of pipes out the other. There is often (and hopefully)
some combination of a hand valve with a spigot nearby to block the flow of
water to make the water with any entrapped air come out into a bucket.
Mark the original position of the balancing
(butterfly) valves on the hex nut next to the slot, or the handle of the
valve. In
the picture below, the slot is on the top left bulge of the fitting.
· You find purge and balance cocks soldered into the tubing that brings water through the radiation. The left-hand side of the picture has a little screw slot on top of the hex nut to turn the paddle inside the valve across the stream of water to partially close the valve. The slot indicates the position of the paddle inside.
· The paddles are inside to force water from the least-resistance pipe on one circuit to the greater-resistance pipe length on another circuit. This is checked by turning the butterfly valve of the pipe length that has less than a 20F drop in temperature from beginning to end until the other length has a 20F drop, so there is even heat. If this was done properly when the system was adjusted for balanced flow, marking the position before moving the slot will let you return the slot to the balanced position.
Turn all the balancing valves so they close the pipes.
· Usually you turn a notch across the pipe with a screwdriver, but some models of balancing valves already have a handle. Make sure the pressure reducing valve is open to the system (Open the feed water valve from the cold water line near the boiler.) Open the boiler drain (purge valve) to let water out until the water runs clear of bubbles.
On the picture above, the purge valve may be a boiler drain screwed into the tapping to the top right. Close the purge valve when the water runs clear of bubbles.
· In some instances, the pressure and flow may not be enough to purge water while allowing water to flow through the pressure reducing valve. A quick fill feature may be on the pressure reducing valve, a bypass might be fitted, or a hose fill might be required.
· Repeat in every loop.
· Reset the balancing valves to their original position.
The fact that boiler pressure dropped below the usual 12 psig factory pressure reducing valve setting is evidence of a leak, so you can add water to the system now to bring the pressure up to force the air out. Watch the boiler pressure to prevent the pressure from rising above 25 psig.
When the pressure is satisfactory, close the isolating valve, then keep watch to see the rate at which it leaks down. If it drops to 7 psig in just a few days, air may be leaving the system through automatic float or wet vents. A description of vents is in the free lessons at http://www.hydronic.net which is a series of easy lessons to help technicians start into the field of hydronics. Try to set the pressure to the minimum again a few times. If the pressure does not stay up after many attempts, the leak is too large and must be repaired.
Keeping the valve closed off, per the instructions on the reducing valve tag, can prevent flooding due to a broken system accessory or line. It is easier to call a plumber to fill the system and flush it of air, as the process can be tricky. An experienced water heating plumber can show you how to do this in the future.
