Water Heater Shopping - How to Pick the Right Unit?
How to pick-up the right water heater for you.
1 Determine your hot water needs.
Work with your plumber to choose a size that fits your needs. The key to selecting the proper model is to know the flow rates of your fixtures, the coldest temperature of incoming water, and your usage patterns (how many faucets do you expect to be able to use at the same time?). You can also install more than one heater to heat water by zone.
2 Understand your dishwasher and clothes washer.
There are appliances that don’t need to use hot water. Just like other washing machine, they could generate hot water internally so supplying hot water for them is unnecessary.
3 Be prepared for resistance from your contractor.
Most contractors don’t want to try something new because of concerns about time and liability. If you are convinced that a tankless water heater is for you, insist on it and find a contractor who will work with you (preferably one who has experience installing tankless units). Provide the contractor with the manufacturer’s installation instructions. You may also want to contact the manufacturer’s technical support department for advice on size and other considerations.
4 Carefully plan the location of your water heater.
Tankless water heaters use an intense flame to heat water on demand. They require more air for combustion and vent more exhaust than conventional water heaters. This affects how and where you install them. There are two ways which you could install them:
Combustion air: A gas-fired water heater (tankless or not) requires a source of oxygen for combustion. To avoid back-drafting that combustion air through another appliance's exhaust pipe, your water heater should be sealed-combustion direct-vent.
Venting: If you are venting through the roof, the length of the vent is determined by the size of the heater (the BTU output) and the number of elbows, or turns, in the vent. You may not be able to vent the heater through the roof if the vent run is long. For direct venting (through the wall), the vent termination must be at least three feet from any operable window.
5 Check your gas and water supplies.
Tankless heaters require minimum water flows for activation. Tankless water heaters can produce three to four times the BTUs a conventional heater produces. Your plumber must verify that your current gas line size, length and even gas meter can provide sufficient gas flow to the unit.
6 Avoid long runs between the heater and the faucet.
It takes some time (a small delay) to heat cold water to the optimal temperature because tankless heaters generate hot water only when you turn on the hot water tap. Locating the heater far from the tap can result in a more noticeable "sandwich effect" when hot water is used intermittently. Using a recirculation pump that brings water from the farthest fixture in the plumbing run back to the tankless heater is one way to overcome this problem. But because these pumps use a lot of energy keeping water in the loop hot, it's better to preheat or buffer hot water.
7 Make sure you meet the building code.
You’ll have a messy and costly fix to sort out later if anyone—you, your plumber or the building inspector—misses a detail during preliminary reviews.
8 Make sure the venting material complies with the manufacturer’s specifications and local building codes.
The venting material for tankless water heaters is specific: it is made of stainless steel and has seals built into it to prevent carbon monoxide from leaking into the home. Double-walled material may be required, depending on your design (be prepared: it is expensive.
9 Be patient and prepare for building department reviews.
There can be a disconnection between the plan review personnel at the building department and the on-site inspector for your project. Be prepared for hesitation and confusion on either end of the permit review and inspection process. Keep the installation specifications and the manufacturer’s tech support number on hand—they can make life easier for all involved in the project.