QUESTION FROM foghat12

I have 3 radiators that when I bleed them nothing but air comes out until nothing comes out at all. 1) Do I need to open the valve that sits on the floor next to these prior to opening the water valve to fill the pipes? 2) Can I open the water refill valve while the system is running? 3) How will I know when I have enough water in the system?

FOLLOW-UP FROM foghat12

two more questions...1) When I checked my radiators last night when the system was idle 3 of them had nothing but air in them. This morning with the system running they now have water and just a slight bit of air. Why is that?
2)while the system is running my radiators "pop" loudly...and in the 3 months I have been in this house the noise appears to be getting louder...any suggestions? (I am new to radiator heat)

ANSWER FROM HOME-WIZARD

Dear foghat12:

Let me answer each of your questions one at a time, and I also address your additional questions from your second posting.

1) Yes, you do need to open the valve that sits on the floor. This is what let's water into the radiator. So when you open the bleeder valve at top of the radiator, air will come out, but if the valve at the bottom is closed, then no water can come into the radiator, and therefore air will come out for a little while then will stop. Some radiators will have two valves at the bottom (for isolating the radiator to remove it from the system), and both of these valves will need to be open when your radiator is operating. This is so the water can circulate through. If this valve is open, and you are still not getting water out, then this could be because the valve is bad, or that the radiator has gotten filled with sludge, and this is blocking the water flow.

2) Which "water refill valve" are you referring to? Is this what you are calling the valve at the bottom of the radiator? Or are you referring to the make-up water valve that brings fresh water into your heating system?

3) There are two things that you need to check to be sure that you have enough water in your system. First, have you bled out all of the air out of the system. And second, does your system come up to the appropriate pressure. Depending on your particular system, this could be around 15 psi. But again, it will depending on the operating pressure rating of your particular heating system.

4) Regarding your problem of your radiators seeming to be filled with air at night when the system is not running, but then filled with water in the morning, I'm wondering if this could be because your pressure is low in your system, and when it is turned off, that it doesn't force the air out. But when the system is running (in the morning), you then have water in your radiators.

5) Lastly, if your radiators are making a popping sound when they are operating, its a little difficult for me to say without actually hearing the sound myself. But perhaps what you are hearing are the sound of air bubbles collapsing. This is something that could happen by the lines at the upper points in a hot water heating loop if the pressure in the system is too low. Which could make sense given the other symptoms which you have described.

Hope this is helpful.
Home-Wizard.com