The systems we see usually have these characteristics:

1. A residential domestic forced-draft gas water heater is used.

2. The space heating water is shared with the domestic hot water supply.

3. The system was installed by unskilled workers

4. The system was not intelligently designed

5. The water heater is undersized for the heat load making it difficult to heat the house in the winter and making cool showers.

6. There are limitations in replacing with more suitable equipment - both structurally and economically.

7. This type of system was typically installed by speculation builders with the cost of the system being the sole consideration - not suitability, longevity, safety or reliability. They went cheap upfront but the cost to run them and service them is higher than it could be.

These water heaters were never designed to heat houses.

The systems we see in Seattle Townhouses usually look like this and have these characteristics:

They are light-duty intermittant-use domestic water heaters. They were engineered to heat water for the shower, sink and laundry. They are built to heat water for up to an hour and then turn off until the next use.

When used to heat the house they can run 24 hours a day continuously during the winter. The machine gets overstressed. They tend to be undersized for the function. Most town houses have a supplemental heat source - a fireplace insert in the living room. We have seen metal fatigue, burner destruction, flue baffles crumbled onto the burners, pilot wiring fried, inducer motor housing melted, flue pipes cooked until they crack.

Needless to say, as service mechanics we do not think that these machines are reliable or predictably safe to operate when used as combination heating/domestic water makers.

They are expensive to fix and most plumbers do not know how to diagnose the problem as most problems are electrical control problems associated with the inducer fan, pressure switches, aqua-stat sensor, or electronic valve.

The life expectancy of these units is less than if the water heater was used for domestic water only. Many of these units are replaced in as little as 5-6 years.

This one is put together a little better than some but it is still underpowered and it needs a heat exchanger to separate the radiant water from the domestic water.

Bacteria Risks: When there is no need to heat the radiators, the circulation pump turns off, leaving water in the radiant piping and radiators to sit and become stagnant, sometimes for months. When the heating season starts, all that stagnant water gets pumped into the domestic tank, contaminating your shower, lavatory and kitchen faucet water with high levels of bacteria.

This picture shows a couple of zone valves which shows some attempt at real temperature control of the radiant loops, which many installations lack.

Many of these installations position the equipment in an inside utility space (not on an outside wall) so there are serious restrictions with retrofitting a larger or different type of heater and/or flue pipe or increasing the size of the gas pipe.

Installing a tank-less water heater as a replacement requires a bigger gas line and a different size or type of flue pipe.

If replasced with a tankless type hot water heater, it should be rated for continuous duty. In other words, a high efficiency hot water boiler should ideally be used.

Contact Seattle Hot Water Company if you would like an expert to evaluate your options with this type of system. We have licensed plumbers on staff that are familiar with both the radiant and the domestic aspects of these combination heating/domestic hot water systems.

Bradford-White equipment is most commonly used in Seattle town house systems.