# Filling a Cast Iron radiator system



## 8 Ball (May 17, 2008)

It would be best to instal the bathroom radiator first, or instal ball valves or gate valves if you have room so you wont have to drain the system again.

Turn the water on and allow the system to fill. When you cannot hear the water flowing into the system anymore, open each bleeder until water flows out consistently. If you have a bypass around the water pressure regulator, opening it will speed things up. Dont forget to pull the pressure relief on the boiler to make sure the boiler is full. When you have bled out all the radiators check the pressure gauge on the boiler, your looking for 12psi lift the relief if the pressure is too high. When the pressure is right turn the power on and let the pump run. Let the system run for an hour or so then turn the power off and bleed it out again. Your system should have 12psi when it is cold and no pump running. If your expansion tank is in the ceiling, and has a glass on it the water level should be at least half way up. If your tank is located on the piping near the boiler you dont have to worry about it. Once the boiler is hot, be careful not to add too much cold water too quickly, cast iron will crack if if you hit it too hard with cold water. 

When your bleeding, work from the lower levels up.

Good luck.


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## Marvin Gardens (Sep 30, 2008)

Remember this. Air rises. All the air in the system will to to the top.

What this means is that it will go to the top floor and it will go to the top of each radiator. Every radiator will have to be bled. If you bled them well then you will have less noise it the radiators. Also do you have an air scoop in the system?

As for capping off the one in the bathroom this is fine. But remember. When you are ready to put that one in the whole system will have to be drained. And make sure you open the basement drain and then open the air vents in the radiators. If you don't do this you could get an air lock that lets loose in the middle of the installation process and you would end up with a lot of water in the new bathroom.


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## Marvin Gardens (Sep 30, 2008)

Forgot to address the filling.

A hose works fine. There should be a valve of some sort to put in the water.

Charge the water, open the valve, then to to the highest radiator and open the bleeder valve. Wait till you get some water coming out, (most bleeder valves have the ability to put a small hose on there to bleed it into a bucket.

Once the top is putting out steady stream of water close the bleeder valve and repeat the process on every radiator.

The go to the top radiator again and make sure that there isn't any air that got in the system.

Then go to the basement and shut the valve first, then shut off the water. Not the other way around for reasons I won't get into.


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## insulatorpro (Aug 21, 2008)

THANK YOU! Got it filled and all seems to be working fine. I'm getting water out of all of the bleeders ( took a while!) All are holding heat and not making any noise. I did cap off the one for the bathroom and its not leaking. When I'm ready to install that, whay do I have to redrain the system? Its not a big deal to do so, just curious. It seems to me that if the system is shut down and the water supply is off that there should be no pressure going to the second floor. All supply and returns for each radiator are independant in the basement. Will backpressure from the others push up through that line? THANKS! 
MIKE


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## Marvin Gardens (Sep 30, 2008)

insulatorpro said:


> THANK YOU! Got it filled and all seems to be working fine. I'm getting water out of all of the bleeders ( took a while!) All are holding heat and not making any noise. I did cap off the one for the bathroom and its not leaking. When I'm ready to install that, whay do I have to redrain the system? Its not a big deal to do so, just curious. It seems to me that if the system is shut down and the water supply is off that there should be no pressure going to the second floor. All supply and returns for each radiator are independant in the basement. Will backpressure from the others push up through that line? THANKS!
> MIKE


Water seeks it's own level. If there is ANY water above the pipes you are working on then it will flow out at that point. Even one radiator on the second floor is higher than the pipes coming out the bathroom floor and all that water will run into your new remodeled bathroom.

If each radiator has it's own system that is totally shut off from the other radiators (by shut off I mean a valve that can be close to keep water from going into the radiator you are working on) then there is no need to drain the system. But if they are connected together without any way to isolate the radiator you are working on then you have to drain the system to below the level you are working in.

Most old radiator systems do not isolate themselves from one another.


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## tk03 (Sep 30, 2008)

In a two story home you will have about 5 psi on the second floor.


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## Nestor_Kelebay (Jun 17, 2008)

Insulatorpro:

When you want to reconnect the bathroom radiator, you'll have to drain the water level in the system down to below the elevation of that radiator.

SAVE the water in 5 gallon pails. Adding new water to a heating system unnecessarily isn't good for it. The new water will contain dissolved oxygen and calcium and iron ions (which make water "hard water"). The dissolved oxygen you add with new water goes either into making O2 gas once the water heats up, or making Fe2O3, which is rust inside the iron boiler or iron piping. The calcium ions in the water you add go into making "scale" in the hottest parts of the heating system (which would be the bottoms of the sections in the boiler).

So, it's better to save the old oxygen depleted an ionically dead water than to put in new water.

In my humble opinion, the BEST way to fill a hot water heating system is to:

1. Remove the highest elevation air vent in the heating system and screw in a 1/8 inch NPT nipple.

2. Now screw a 1/8 inch NPT ball valve on to that nipple.

3. Now screw in a standard coin air vent into the top of that nipple, but don't use any teflon tape or pipe dope.

Most of the time that assembly can be used as an air vent to release accumulated air in the radiator by opening the ball valve and opening the air vent until it starts to leak water.

However, during those times when you want to refill your heating system with old water, you just:

A. Stand a chair next to that air vent

B. remove the air vent from the ball valve and screw in a 1/8" NPT by 1/4" hose barb fitting

C. set a 5 gallon pail with old heating system water on the chair and siphon that water into the hose barb fitting (with the ball valve open).

D. Now, open all the other air vents on the heating system until water bleeds out of them.

That way, there's never any chance of the water pressure in the heating system becoming too high.

After siphoning the old water back into the heating system, add sufficient water from the feedwater make up line to raise the system pressure to about 12 psi (as shown on the boiler's pressure gauge). That's a recommended pressure. Going too much below that MIGHT result in cavitation of your circulating pump's impeller.

AND, if you ever have the opportunity to redo the water make-up line to your boiler, the best way to do it in my opinion is with a pressure gauge, garden hose silcock (pointing up instead of down) and ball valve all immediately down stream of the pressure reducing valve. (Also, install a bypass line to add water quickly by bypassing the pressure reducing valve.)

The advantage of this piping is that it avoids the common problems associated with setting the pressure reducing valve. Often, it will take hours for the pressure reducing valve to fill the system to the correct pressure, and so people aren't sure if the pressure setting on the reducing valve is correct. They can open the main valve on the feed water make up line and come back 4 hours later to find the pressure is 28 psi!. By having a pressure gauge and ball valve immediately down stream of the PRV, you simply have to close that ball valve and turn the adjusting screw on the PRV until the pressure reads 12 psi. Because of the very tiny volume of water that has to be added, the response on the pressure gauge when the PRV screw is turned will be instantaneous.

And, since most PRV's have check valves built into them to prevent cross contamination of boiler water with potable water, if your PRV setting is too high, you can simply open the sillcock downstream of the PRV (but upstream of the ball valve) to release the water pressure, unscrew the adjusting screw on the PRV a bit, and try again. Once you have the PRV raising the water pressure to 12 psi in that tiny volume upstream of the ball valve, you can then open the ball valve and be sure that the PRV will raise the whole system's pressure to exactly 12 psi.

Instead of a silcock, you could also just use a ball valve with a drain cap on it. Just make sure the drain cap is pointing up so that you never introduce air into the piping when releasing the pressure.


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