Low flow fixtures are one of the tools being used in residential water conservation. They are of course mandated, and you can’t buy residential plumbing fixtures that are not low flow. Tankless water heaters are all the rage for saving energy. Combine the two and see what happens.
Low Flow Fixtures
Obviously low flow fixtures are not a panacea. They don’t save you water if you are filling a pot, getting a glass of water or any use where a fixed volume of water is needed. They can be a nuisance when you have to wait and wait for that pot to fill with water, or if you are trying to get hot water to the sink.
Low flow fixtures slow down the velocity of the water traveling through the pipes, and consequently it can take considerably longer to get hot water from the water heater to the fixture with slowly traveling water. This is especially annoying when you have long pipe runs.
It can even lead to water wastage. It can take so long to get hot water at a fixture that some homeowners turn on the hot water, and then go do something else before returning to use the hot water. By the time they return and find that hot water is being dispensed they are running hot water down the drain. So now they are wasting energy as well as water and the energy is much more expensive than the water itself.
Tankless Water Heaters
Tankless water heaters are becoming very popular these days, and when you combine low flow fixtures with tankless water heaters you begin to experience some problems. To begin with tankless water heaters already take longer to deliver hot water to your fixtures than tank type water heaters. They have to first heat the water, while tank type water heaters already have a tank full of hot water ready to go.
Since a minimum flow rate is required to turn on a tankless water heater you can’t turn your hot water faucet on with a trickle or low flow of hot water because it won’t turn on the heater. If you need a low volume flow of warm water you will have to first turn the faucet on with enough flow to turn on the heater. Then you will need to add cold water to get the temperature where you want.
If it turns out you need half cold and half hot water mixed to get your desired temperature, then you will need 1 to 1-1/2 gallons per minute minimum flow. This creates a serious potential scenario for wasting water. Also, if the fixture is limited to say one gallon per minute or less you simply may not be able to get the temperature of water you want for those low flow streams of water without changing the outlet temperature setting on the tankless water heater. Don’t forget to set it back to the original temperature setting before getting in the shower though.
Hot Water Demand Systems
One way to overcome the inconvenience of low flow fixtures when trying to obtain hot water, especially with those long pipe runs, is a hot water demand system. Hot water demand systems pump the water to your fixture at high speed without running any water down the drain. You not only get more convenience but you save a ton of water as well.
Demand system use very little energy since the pumps only run for a few seconds and only when you demand hot water. Typically for a 4 person household the energy usage is less than $2.00 per year in electricity to run the pump.
Hot water demand systems are great when paired with tankless water heaters. With such a combination you save energy with the tankless hot water heater and water with the demand system. It is a great way to go green with your residential plumbing system.