Instant hot water heaters
Instant or tankless hot water heaters can be an energy saving solution for heating your water.
Tankless gas water heaters are energy-efficient. However there are some “gotchas” that can make them unsuitable for some situations.
Tankless water heaters are “on demand”,Â heating water only when required. This saves energy, compared to a conventional tank type heater.
Advantages compared to a conventional tank type water heater are:
- Eco-friendly in that it saves energy.
- Unlimited hot water. These units can deliver hot water for hours and are not limited by the tank capacity.
- Constant temperature, don’t get cooler as hot water runs out of the tank.
- Small. Can be mounted on wall, freeing up floor space.
- May qualify for tax credits.
Disadvantages of Tankless Gas Water Heaters
- A few seconds delay before hot water starts flowing. This can make brief uses like washing hands impractical and water is wasted, waiting for the hot water to flow, but using several small units and placing them close to the point of use will reduce this problem.
- Heater may switch off if flow rate is not high enough. Low-flow shower heads may not draw enough water to trigger the heater. The same goes for trickle applications like shaving and you can end up using more water just to keep the heater on.
- Limited heating capacity. Might not heat water to high enough temperature in winter, depending on required flow rate of water. Some models have a specified minimum inlet water temperature (example: 60 degrees Fahrenheit).
- Needs more maintenance than tank water heaters. Valves may need cleaning or lubrication every year, replacement every few years.
- May need larger hard line (not flexible) gas pipes (3/4 inch), water pipes (3/4 inch) or vent pipes (5 inch).
- Some models require stainless steel venting (not galvanized steel), which can be expensive.
- May need a higher gas pressure. Gas pressure in some locations can be too low. This needs to be checked with a manometer.
Sizing Tankless Gas Heaters
Maximum water flow rate for tankless gas heaters range from 2 to 7 gallons per minute (gpm). This is with a temperature rise of about 45 degrees Fahrenheit in the outlet water. Flow rate can be increased at the expense of lower outlet water temperature. 2 gpm is considered too low for most home use (except maybe in summer), with 4 gpm the minimum recommended by many manufacturers for a single application (shower or dish washer or clothes washing machine, one on at one time). 6 to 7 gpm is recommended for two simultaneous uses.
Computer controlled heaters allow thermostat control of water temperature, providing constant temperature water even if the water flow is turned up or down. However they can be less reliable, requiring good operating conditions (water pressure, gas pressure). They also run off mains electricity supply, and will not operate if there is a power blackout.
Choosing the right tankless gas water heater can be complicated, especially when piping and venting requirements are considered. We suggest that you consult Dial A Plumber before deciding which unit to buy.
WeÂ will also be able to advise you which brands we can service most econmically (since many heaters need annual maintenance), which brands have a good reputation for reliability. Buying a heater that can’t be serviced would be a waste of money.
Contact Dial A Plumber now for the best information on buying and maintaining instant hot water systems. Call us now for more information or to schedule an appointment – call any of the numbers at the bottom of the page for sudden hot water service!