Testing Pipes on an Inactive Hot Water Boiler System

My wife and I are contemplating the purchase of an 80-year-old home with a hot-water boiler system that has been inactive (empty) for 30 years. We know we'll have to replace the boiler with a new, high-efficiency model to heat the 7,500 sq. ft. of space. Because the system is currently inoperable we haven't been able to test the pipes and radiators. Any guess on whether they might still be functional given this history? Any thoughts on the cost of replacements?

Thirty years is a very long time for a heating system to gather dust. Theoretically, if every drop of water was removed from the supply lines and radiators, and the house remained bone dry, the plumbing could be intact. Or not.

All those heatless winters and humid summers have probably had some effect. There's always the chance a pipe has developed a pinhole leak or a radiator containing some residual water cracked in a midwinter deep-freeze.

In new construction, plumbing systems are typically pressure-tested with air at least overnight to make sure they don't leak. That might be an easy way for your heating contractor to find out whether the system still holds water.

If you discover the hot-water supply pipes or radiators are suspect, you won't have much choice but to repair or replace. That's going to make a mess. And if you really need a house that big, it would make sense to consider a number of energy improvements at the same time.

When the house was built, energy was absurdly cheap. Now it's not. A high-efficiency boiler can help, but without enough insulation, modern windows, and a concerted effort to seal air leaks, the house will suck up an enormous amount of fuel. And you could still need an extra sweater in the winter.

Given that reality, it might be prudent to contact a renovation specialist along with a heating contractor and get an estimate on what's called a "deep energy retrofit." Money you invest in reducing the amount of energy you need can pay handsome dividends in the future.

That also shrinks the size of the new boiler, along with reducing the number of radiators you're going to need. It won't be a straight trade, but it helps offset the cost of updating the heating system.

New boilers, especially a type called modulating-condensing boilers, are a marvel of efficiency compared with the dinosaur you're looking at. The best of them are more than 95% efficient. But getting the heating load as low as possible is the best first step.

When you do get around to ordering a new boiler, make sure your contractor uses something called "Manual J" (or its equivalent), which is software produced by the Air Conditioning Contractors of America for sizing heating and cooling equipment. Old school guys sometimes like to guesstimate those things, but you don't want to go there.

As to cost, it's anyone's guess. None of this is going to be cheap. But if you plan to stay in the house, spend now and save later.