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Replacing a cast iron radiator

I have a house that was built in the 1940s. My heating system is a circulating hot water system with cast iron radiators. I was remodeling the bathroom and had the old radiator removed for blasting and powder coating. After the radiator was powder coated, a pin-hole leak was discovered. Everyone advised that I don't try and have it fixed. Since then, I've been trying to get some sort of replacement.

One contractor is saying, only use another cast iron radiator system. Another contractor is saying I can use a low profile radiator (picture looks like a slant-fin baseboard) that is stainless steel. I can't figure out who to believe. I'm concerned the baseboard will not provide adequate amount of heat.

The bathroom is small, 52 sq ft. One other complication, I have to work with the existing piping which are 36 inches apart, so maximum length of the system is about 30 inches. BTW, I live in southern Virginia, where the winter temps don't normally go below 25 degrees.

What questions should I be asking? Will a small baseboard system work in this room? Can I mix the baseboard system with the cast iron radiators?

Thanks for the help.

Re: Replacing a cast iron radiator

What you should be asking is what was the BTU output of the radiator. And what the BTU output is per ft. of baseboard. I think what you will find is that you don't have enough wall space for baseboard to equal the output of the radiator.


Re: Replacing a cast iron radiator


Yes, John makes some good & important points about the size of the original radiator & the amount of heat it put out, which would be considerably more than 2 or 3 feet of baseboard, which would put out approx 1680 BTU/hr (assuming 1 gallon per minute hot water flow @ 180 degrees) where the small bathroom may need between 2000 & 3600 BTU/hr, not only to heat the bathroom, but to allow the house occupants to feel comfortable after a shower on a cold winter morning; there are numerous options to this & you don't have to use just 3' of baseboard, or be restricted to fitting something inside the 36" space between the existing piping you have now; in addition, there is HIGH OUTPUT baseboard available & you may have enough total footage along the base of the bathroom walls to install enough high output baseboard, or a kickspace heater.

I wonder, Kari, if you would adjust your personal account so you could accept private messages (PM) or Email from other members; click onto User CP at the top of the page; then onto Edit Options, then onto Messaging & Notification---->Receive Email from other members------>Enable Private Messaging.

Sometimes you're better off having a contractor do this work-----there are a number of factors involved that can throw a DIYr off track because of the tricky heating variables that are involved in putting in a different type of convector (baseboard, smaller rad, kickspace, stainless steel towel warmer, wall-hung stainless steel convector, etc.)

Another issue here is how the bathroom piping supply & return connections are piped in relation to the boiler & how hot is the water running thru the piping by the time it gets to the bathroom & how many gallons per minute are flowing thru the pipe----many times the bathroom rad is the LAST convector on the circuit to get the hot water from the supply being pumped from the boiler, which means it's not as hot as the supply to the rads in the other rooms----can you tell us if you feel that there was ENOUGH HEAT in the bathroom in the past when you had the radiator that now leaks in place ?????-----if there was enough heat from the old rad, you can calculate the rating of the old rad & replace it with one the same size or larger, or perhaps use a kickspace heater if you can't find a 2nd hand rad. Is there insulation in the exterior walls of this bathroom (assuming it is near the exterior of the building), and are the windows in this bathroom double-pane or fitted with storm windows; does it have normal 8' ceilings; does it have a cabinet type wash basin with a wood base (that would hold a kickspace heater); does it have a standard cast iron bathtub ?????

Other options you might consider, if the old radiator (pin hole leak) is unusable is to consult the Yellow Pages under Demolition Contractors, Used Heating Parts, Used Plumbing Parts, etc. to find a 2nd hand rad of approx the same size as the old one; there are sites to refer you to, but the system won't let me list them until I have more posts; there is a way of measuring the amount of BTU heat output of a radiator, according to its size, the number of sections it has, etc., to determine its BTU output; a HEAT LOSS calculation is then done to determine how many BTU of heat per hour are needed to keep the bathroom warm on a cold winter day.

If you DO find a 2nd hand rad in your area, ALWAYS HAVE A PRESSURIZED AIR TEST done before you buy----this is a rather simple procedure where you block off one side of the rad with a screw-on metal fitting (compression fitting) then attach a bicycle pump with a pressure meter to the other side & pump approx 12 lbs of air into the rad-----the needle SHOULD HOLD STEADY for a minute or two to indicate there is no leak in the rad being tested----if the needle drops, reject the rad---the place where you buy the rad may have a test stand where they test the rad on the spot while you watch.

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