How bad is a radiator leak in a hot water cast iron system?

centuryhomeNY · January 27

I live in an 1890s house. We have the original hot water radiators made of cast iron and a gas combiboiler just installed this summer, prior to that there was an oil boiler dated prior to 1967.

A few weeks ago I noticed a water spot under one of the radiators, so I put a rag down while my husband added it to his list of things to fix. This week we upgraded to a Tupperware and yesterday it was all the way filled, and this morning it filled again. So suddenly we’ve gone to losing about 3-5 cups of water in 24hrs.

We have 5 radiators, 1 is on this same line directly above and has no issues. The leak is at the joint on the side where there is a knob, so I assume intake? My husband had just announced that between the many paint layers and visible corrosion this is a plumber job. We’ve called and are on a wait list.

How big of an issue is this? Is this leak causing damage to the larger cast iron pipe system, or to the new boiler? If we are quoted thousands to replace the ancient radiator and splice it into the ancient system is it something we need to do urgently?

Intplm. · January 27

Please post some pictures. Some close up and farther away.

Gabriel82 · January 27

@centuryhomeNY In any heating circuit there should be no leaks of any kind!

Especially when using antifreeze mix in the whole system...

And in cast iron there's nothing to do but change the radiator.

I know some guys can weld any cast iron(even engine blocks) and last some time, in this case it's not worth it.

If the new boiler is condensing type ,the radiators must cool down the water to around 100-105 Fahrenheit so condensing can occur and get those few percentages of efficiency from the boiler.

If it's a normal,non-condensing type boiler just change the radiator with a better one and its all good.

I would check the quality/chemical composition and PH of the water used in the system/boiler!

Helps the boiler work better in the long term.

Nevermind the pumps...

Any debris,rust in the water/system can damage the pump impeller or even the boiler!

I always keep it clean in my gas fired boiler.

Change the whole water/antifreeze mix every 2 years as in a car.

So far no bad radiators.

And I did had about 30 years ago cast iron radiators.

Because of constant rust found in system I changed them to simpler steel ones.

Was attracted by aluminium ones but at the time didn't trusted the products…

Maybe in the future will try them.

But condensing boiler are becoming fast the new norm and they require special forced air cooled radiators.

Might be forced to go that way...

If the plumber does come to your place ,checking how clean water is in the system or the PH would be a good thing!

Might not be the last leaky radiator...

Especially if they're old and the water dirty(electrochemical galvanic corrosion can occur with time!

Least noble metal gets corroded with time…

Jamie Hall · January 27

As has been said, any leak is a problem.

However, how much of a hassle it is depends on exactly where the leak is. For instance, if the leak is from the valve stem, it's an easy fix. If the leak is from the valve threads or from where the pipe, called a spud, screws into the radiator, that's a bit more of a pain (it can be a big pain, but doable) it can be repaired. However, if it is between sections of a hot water radiator… not much hope there.

Is there a chance you could post a picture point out exactly where the leak is?

How bad is a radiator leak in a hot water cast iron system?

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