Home Care Library
Radiator Low Water Level
The Home Wizard app calculates your ideal home care program to avoid problems with your Radiators, but sometimes trouble can still occur. Here are answers to questions about radiator low water level.
QUESTION FROM Tim P.
I own a top/down duplex, where the top unit (2nd and 3rd floors) is heated by hot water radiators. We recently had an incident where the tenant allowed some (drinking) water pipes to freeze and at the same time, we noticed that the carpet beneath two of the three 3rd floor radiators was soaked. There were ice crystals on one of them. The third radiator seemed fine, just not hot. After getting the furnace going for a couple hours and watching it to check for possible burst pipes in the heating system, everything seemed OK until about two days later when my tenant reported that there was a 2-inch diameter hole in one of the two radiators (not the one with ice crystals). Everything was dry. The pipe to the left side was warm, the pipe to the right was significantly hotter, but touchable. The other two radiators were both hot and seemed normal. I'm not sure if there are zones involved here, I see only one gauge on the furnace for pressure/temp. Only two main lines run from/to the furnace, and split at different points in the basement to run through the ceiling.
I'm thinking I will have to just replace the entire radiator. My questions.. 1) why did nothing leak out of the radiator? is there some sort of automatic pressure detecting shut-off valve? 2) Will this be something I can handle myself? There is one valve on the left side pipe with a nut and what looks to be a flathead screw, however the screw does not turn at all. I do not see any other valves for this radiator, or anything in the basement aside from the main valves on the two big pipes coming from/to the furnace.
Thanks, hope the details were worth it!
ANSWER FROM HOME-WIZARD
Dear Tim P:
What I suspect might be happening is that when your heating system pipes froze and burst, your heating system lost water. Normally, this water is made up in the system if you have an automatic water make-up valve. Two things could be happening that could have prevented the make-up water from coming into your system: 1) you have an automatic water make-up valve, but it is not operating properly; or, 2) you have a manual water make-up valve, and it has not been opened. If the water level in your system low, it could be possible that the water is no sufficient to reach the level where the hole in the radiator now is (especially since it sounds like this radiator is on the top floor). This could also explain why the pipe is hot on one side of the radiator, but not on the other side. So you will want to check to see whether or not you have an automatic water make-up valve, and if it is operating properly.
If it helps, if you look at Figure 5-3 of this webfile, it shows how you could have radiators in different floors of your home, and how low water level could keep hot water from reaching the top floor radiator:
Regarding your second question, here is a video that describes how to replace a radiator:
Hope this is helpful.
Thanks for the quick response and the literature.
I got the pdf and will be reading through it. The thing is though, that the heating system pipes didn't burst, it was the regular water line with the issue.. although the radiators were freezing at one point, I don't see any evidence of that causing broken pipes. I guess it's possible that the water level has been low for a while, but doesn't the water circulate through the radiators, and so there would be water coming out if the radiator was in operation.. Well I have some reading to do, so maybe that will help. Ultimately, I'll replace it anyway.
Dear Tim P:
I guess what I was thinking is that when you said the carpet was soaked underneath two of the three radiators on the 3rd floor, that the water had come from these two radiators (for example, when the radiators froze that they either created the 2-in gap, or split at a seam, or opened up where valve thread into piping, etc.) And this water leaking out is what then resulted in the water level of your heating system becoming low.
And when you get a chance to look at Figure 5-3 in the literature, it will show how you can have radiators that are in "loops," such that if the water level is low, that it is possible that water does not get to circulate to a radiator in a loop up to an upper floor, because the water level is too low (not enough volume) to circulate up that high.
Also, if you get a chance, please look at the question and answers that I had with "Nance Lee" regarding the 2 inch diameter hole that she had in her radiator. You can find this in the Question & Answer section of the webpage on "Radiators" in on online Maintenance Library around the dates of 2/20/08 to 2/21/08:
When you had mentioned that your tenant mentioned a 2-inch hole in the radiator and the carpet was soaked underneath it, I had initially assumed that this was caused by the radiator bursting (and this is how the carpet got soaked). But now I'm wondering if your 2-inch hole is a manufacturing hole (similar to Nance Lee's), and the water from your radiator instead came from a split or valve thread opening up, etc.
But either way, now your problem is that your water level in your heating system is low, and you may have a radiator or piping (with possibly two radiators) that could start leaking when your fill you system all the way back up.
In other words, please be very careful when you start adding water back in!
Hope this helps. Please let me know what you find out, and we can continue to try to work the problem.