subject: Water Conservation, Low Flow Fixtures, and Tankless Water Heaters [print this page] Low Flow Fixtures Low Flow Fixtures
Now days, all faucet fixtures for residential plumbing are low flow devices.
While low flow fixtures do aid in water conservation efforts, they can be a bit inconvenient. They dont save you water if you are filling a pot, getting a glass of water or where a measured volume of water is to be had. They can be a nuisance when you have to wait and wait for the sink to fill with water, or if you are trying to get hot water to the faucet.
Low flow fixtures cause the hot water to flow through the pipes more slowly, and so it takes longer to get your hot water. This can be especially frustrating when you have long pipe runs, or when your pipe is under a concrete slab and not insulated.
Slow hot water can lead to water wastage. It can take so long to get hot water at a fixture that many hot water users let the hot water run while they do something else before returning to see if it is hot yet. By the time they come back and check they are running hot water down the drain.
At this point energy is being wasted as well as water and the energy to heat the water being run down the drain is substantial much more expensive than the water being heated.
Tankless Water Heaters
Tankless water heaters are not water conservation friendly to begin with. It takes a tankless unit longer to deliver hot water than a storage water heater since it has to heat the water first which can take 10 to 20 seconds longer than a storage water heater would deliver it.
To obtain the hot water temperature you desire you typically mix hot and cold water to get the desired temperature. This works fine with a storage water heater but can be a problem with tankless units when lower flows are used.
To turn on the tankless heater you must draw to gallons per minute, depending on the water heater model you have. The outlet temperature with a tankless unit does not change as long as you dont exceed the maximum flow, so the minimum flow of say gallon per minute is at the full outlet temperature.
If you need to mix half cold and half hot to get the desired temperature you are then forced to use 1 gallon per minute which can often be a much larger flow than you need or want. This of course results in wasted water being run down the drain.
Hot Water Demand Systems
Hot water demand systems can overcome the inconvenience of slow hot water caused by low flow fixtures. Hot water demand systems pump the water to your fixture fast without running water down the drain. Your hot water is faster and you save time water and money.
A hot water demand system typically locates a small pump under the sink furthest from the water heater. When hot water is desired the user pushes the start button which activates the pump and speeds hot water to the fixture. The cooled off hot water from the last hot water use is returned to the water heater through the cold water piping so no dedicated return line is needed.
Demand systems are especially nice when used with tankless water heaters since you save both energy, with the tankless heater and water, with the demand system while having the convenience of fast hot water.
Water Conservation, Low Flow Fixtures, and Tankless Water Heaters
