Question: About three years ago, my husband and I gained some space to enlarge our bathroom by getting rid of our old water heater that was in a hall closet and having our plumber install a new tankless water heater on the outside wall of our house.
It worked just fine for the first couple of years, but recently the water is not getting as hot as it should be.
After turning the temperature setting up to the highest level, the water warmed up a little but still is not as hot.
I paid more than $3,000 to purchase the tankless water heater and to have the plumber install it, so hopefully it isn’t already worn out.
Any ideas as to what the problem might be so we can enjoy a nice hot shower again?
Your Handyman: Tankless water heaters have been used in Europe for many years but are a relatively new appliance here in the United States. They have received a great deal of attention as a “green” option for heating the water for your home.
Unlike the conventional water heater that keeps 40-50 gallons of water constantly hot in an insulated tank, the tankless heater has a sophisticated copper heat exchanger fueled by natural gas or propane that doesn’t fire up until someone opens a hot water valve inside the home. As a result, no energy is spent keeping water hot that isn’t being immediately used.
This copper heat exchanger is very susceptible to mineral scale buildup, much like a tea kettle, and it is best that the house has a water softener or, at a minimum, a particle filter plumbed in line before the heater.
If your home does not have a water softener, minerals will build up sooner in the heat exchanger, which may make it heat water less effectively and, over time, may possibly cause the unit to fail.
Most manufacturers of tankless water heaters recommend that the unit is flushed annually to remove mineral buildup, and some make an annual flushing a requirement of the warranty for the heat exchanger.
The flushing process is actually pretty simple, and the secret ingredient is plain old white vinegar that can be purchased at any grocery store.
If you chose to do the flush yourself, you will need a clean five-gallon plastic bucket, a pair of water supply lines similar to what are used for a clothes washer, a submersible sump pump, and 2-3 gallons of white vinegar.
Your first step is to turn off the tankless water heater at the control panel so it can’t turn on while being flushed. Next you will want to identify and close the isolation valves that control the cold-water supply into the heater and the hot water supply out of the heater.
On the base of the unit will be two ¾-inch male threaded fittings with screw-on caps, one on the cold intake side and the other on the hot supply side, and to these you will connect your two hoses.
Each of these fittings will have a valve that you will turn to the open position.
The end of the hose attached to the cold supply side is now threaded onto the sump pump, which is sitting inside the five-gallon bucket and the other hose end is put loose into the bucket.
Pour the white vinegar into the bucket, turn on the sump pump and let it circulate the vinegar through the heater for about 45 minutes, which will effectively descale the heat exchanger.
Next, remove all the vinegar from the unit by circulating clear water for about 10 minutes and the flush is complete.
You can also do an online search for “how to flush a tankless water heater” to find countless how-to videos on the procedure. Or if this is not your idea of a fun thing to do on a Saturday morning or on your day off, most any handyman service or plumber can be hired to do it for you.
