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You need a decent pump to pump the anti-freeze into the system. It must produce in excess of 15 psi with a drain valve open while you purge. We use booster pump ($400-$600) but a good quality utility pump can also do the job.
You connect the pump outlet to the main boiler drain at the bottom of the boiler. Then connect a hose (we use washing machine hoses) to the drain valve on the purge station and drop the other end into the bucket/reservoir with your glycol/water mix. We use a 2 parts glycol to 1 part water mix. This allows you to top off the pressure with the boiler water feeder should the pressure drop down the road without having to drag out the pump again. You turn on the pump then open the main boiler drain to start to fill the system. Our pump set up has a ball valve on the pump outlet so we can quickly and easily shut off the flow into the boiler (without having to close the drain valve) as we shut the pump off. You need to watch the reservoir making sure it doesn’t get too low or you’ll suck air into the system.A purge station is typically a shut off with a hose drain valve above it. There can be 1 piece purge stations where both the shut off and hose fitting are combined in one piece. Or it can be a separate valve (shutoff) with a hose type "faucet" (we call it a boiler drain) above it. They are usually at the boiler on the pipe above the circulator pump. You need to determine which one goes to your problem area. I have seen purge stations in old systems some distance from the boiler on the heating line (pipe). Be sure to turn the power off to the boiler while you are purging and it’s best to let the boiler cool down to around 100 degrees (if it’s currently hot) before purging. Dumping a lot of cold water into a hot boiler is not beneficial.
You need to shut the valve on the purge station. Some all-in-one fittings close the valve and open the hose at the same time so be sure your hose is attached first if you have one of these fittings. If you have zone valves with multiple purge stations all the zone valves should be opened manually. The common theme here is that you want to push the mix through the loop and have it come out the purge station drain. If you don’t stop the flow below the drain no air will be purged. You don’t want the mix to go directly from the boiler then out the drain/hose. Closing the shut off next to the purge station drain forces the water through the piping loop/zone. If you have zone valves and only 1 purge station then you need to open the zone valves one at a time and fully purge a zone before opening the next valve and closing the valve you just purged. You need to maintain the pressure (at least 10-15 psi) while you are doing this but you need to keep the pressure under 30 psi.
You need to let the water run until you hear no more bubbles coming out of the hose for several minutes. You then shut the purge hose off at the same time you shut the main boiler drain and the pump off. Then open the purge shutoff. Be sure the pressure on the boiler is between 15 & 20 psi when you are done and before you turn the power back on. This is a bit higher than normal but it allows for the residual air in the system to vent out the float vents without the pressure dropping too low since you should have the water feed to the boiler shut off. The boiler you have has no bearing on this process. It is the same what ever type you have.
Here is an example of a suitable reasonably priced pumphttp://www.homedepot.com/p/Wayne-1-2-HP-Cast-Iron-Portable-Transfer-Utility-Pump-PC4/100067909