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Dual-Valve Device Blocks Flooding in Water Heaters


QUESTION: Is there any device available that would protect against a flood in the event my water heater springs a leak while we are away on vacation?

ANSWER: Yes, a device called Heaterguard consists of a normally closed control valve in the cold water line and a check valve in the hot water outlet. The valves are interconnected by a sensing tube. The normally closed inlet valve contains a diaphragm that separates tank pressure on one side and household pressure on the other. The sensing tube is located above the diaphragm.

Consequently, when there is a household demand for hot water, the pressure differential created across the diaphragm causes the valve to open, allowing cold water into the tank. The check valve opens, and water is drawn out as well.

If a leak occurs, about a pint of water escapes as tank pressure drops to atmospheric pressure. Since the sensing tube is above the diaphragm, there is no pressure difference between the valves, so the control valve remains closed. The check valve in the hot water outlet prevents introduction of air from an open faucet, and the resulting vacuum prevents further leakage from the tank. Little or no water flowing from the hot water tap notifies the homeowner that there is a problem with the heater.

Heaterguard costs about $50 at plumbing supply houses. It's manufactured by Boals Control Co., 11 Conejo Circle, Palm Desert, CA 92260.

Coat Cedar Siding to Prevent Rot

Q: What is the best product to protect cedar siding, especially when it's exposed to severe weather?

A: Western cedar is a very durable wood, but its surface characteristics are quickly changed by the actions of sunlight and water, especially in harsh climates. Although cedar is resistant to rot, it is not immune to it. Sections of cedar siding that are prone to rotting are unprotected end-grain areas and pieces near the ground.

Cedar siding should be coated with a finish that provides water repellency and protection from ultraviolet light. The finish should also contain a preservative that kills mold and mildew. Ideally, the finish should allow the wood's grain to show through. For this reason, penetrating oil-based semitransparent stain is a good choice. It is lightly pigmented and water repellent. The pigments in the stain provide a small amount of protection from the damaging effects of ultraviolet light. You can purchase this stain at a paint store or home center.

Clean the siding and let it dry before applying the stain. Surface cleaning may be done with low-pressure power washing using bleach in the water to kill mold.

Not Enough Hot Water From Tankless Heater

Q: My house's hot water is supplied by a tankless coil connected to a boiler. The system supplies an inadequate amount of hot water. I am about to replace my heating system, and I want to know how to correct this.

A: If you are going to replace the boiler, we would recommend that you do not get one that produces domestic hot water and heat for the house. Our preference is a boiler for comfort heating and a separate water heater fired by oil or gas.

Our reasoning is as follows. Most tankless water heaters consist of a small-diameter coil of pipe inside the boiler. The coil is surrounded by a hot water boiler that gives up its heat to the water flowing in the coil. Cold water enters the coil and leaves with its temperature increased by about 100 degrees Fahrenheit. The system is designed with a flow rate through the coil that achieves the desired temperature.

However, if water flows too quickly through the coil, less heat will be transferred to the water in the coil. Because of this, many tankless coils have a flow-regulating valve installed in their cold-water supply pipe. For example, the design flow through these heaters is usually about three to four gallons per minute. Assuming a normal water supply to the house, the typical cold water flow will be between four to eight gallons per minute.

Water can also flow too slowly through the coil. Over the years, mineral deposits tend to build up inside the heater coil, especially in hard-water areas. This reduces the water flow through the coil. Since a tankless coil has virtually no storage capacity, household demand will frequently exceed the coil's ability to supply hot water.

Pads Can Quiet Noisy Baseboard Heater

Q: We have hot-water baseboard heat, and we get a constant knocking at both ends of the baseboard units when the heat is coming up and also when it's going down. Our house has upper and lower levels and a two-level heating system.

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