Is tankless right for your house
Tankless heaters make sense when you want endless hot water in a smaller footprint, or when a tank takes up room you need. They suit homes where usage is steady rather than packed into one hour. A big household running several showers and the washer at once may need a larger unit or two.
| Question | Tank | Tankless |
|---|---|---|
| Hot water supply | Limited to tank volume, then recovery | Continuous, up to the unit's flow limit |
| Space | Needs a floor footprint | Mounts on a wall |
| Install work | Usually simpler | Often needs bigger gas line and new venting |
| Maintenance | Flush sediment and check the anode | Descale the heat exchanger on a schedule |
| National installed cost | $600 to $3,100 | $1,400 to $5,600 |
What installation involves
Gas tankless units draw a lot of fuel at once, so the existing gas line is often too small. Venting is usually sealed plastic or stainless pipe through a wall or roof. Electric models need heavy wiring and breaker capacity that many panels do not have spare.
We size the unit to your peak flow, check the gas pipe and the panel, and give a clear price before work starts. Compare this with our tank water heater installation if you are still weighing the two.
Weighing tankless against a tank? Call and a plumber will talk through your house.
Call (855) 575-2890Hard water, chloramines and tankless units in Hazelwood
Missouri American Water reported total hardness at its Missouri River treatment plants of 82 to 226 ppm in its 2023 report. That works out to roughly 5 to 13 grains per gallon, from moderately hard to very hard. The report does not say which plant serves which street, so test your own tap or ask Missouri American Water at 866-430-0820.
Hardness matters because scale builds inside a tankless heat exchanger, which has narrow passages. Scale cuts flow, causes error codes and shortens the life of the unit. If your tap tests at the high end, plan for annual flushing and consider a softener, which our water softener page covers.
The water is also treated with chloramines, which can wear rubber seals and gaskets over time. That is one reason we check the small rubber parts at service.
Gas tankless models are listed to the ANSI Z21.10.3 standard, and the manufacturer's manual sets the vent type, gas line size and flush schedule. Follow that manual and keep a record of the flushes, because many warranties ask for proof of maintenance.
Repair and troubleshooting
Most tankless faults show up as an error code, lukewarm water or a unit that shuts off mid-shower. Common causes are scale, a dirty inlet filter, a blocked vent or condensate line, or a failed flame sensor or flow sensor.
- Check the inlet screen and clean it if it is clogged.
- Look up the error code in the manual, since each brand uses its own.
- Make sure the gas valve is open and the vent is clear.
- Call us if the code returns after a reset.
Some faults involve gas or combustion, so we do not recommend more than screen cleaning as a do-it-yourself step. A smell of gas means leave the house and call Spire at 800-887-4173 or 911.
Flushing and descaling
A flush runs a mild acid solution, usually white vinegar or a descaler, through the heat exchanger with a pump. It dissolves scale that has started to coat the passages. Most manufacturers call for a flush about once a year, and sooner in hard water.
Skipping flushes is the most common reason tankless units fail early and the most common reason a warranty claim is denied. Check your manual, because it states the interval and the method.
Tankless water heater cost
National cost guides put a tankless water heater installed at $1,400 to $5,600. That is higher than a tank because of venting, gas line and electrical work, not just the unit. These are national ranges, not a quote.
Tankless units often last longer than tanks, but only if they are descaled on schedule. Add the yearly flush to the cost you plan for.
Placement and permits
The City of Hazelwood contracts with St. Louis County for plumbing permits and inspections, so a tankless installation is permitted through the county. Hazelwood's published winter design temperature is 2 degrees F, so a unit in an unheated garage needs freeze protection, because a frozen heat exchanger can crack. See our water heater repair page for failures, and we serve Florissant as well.
Frequently asked questions
Missouri American Water's 2023 report shows total hardness at its Missouri River plants of roughly 5 to 13 grains per gallon. The report does not tie plants to streets, so test your own tap or call Missouri American Water.
Most manufacturers call for an annual flush, and more often in hard water. Check your manual for the exact interval and method.
National guides put it at $1,400 to $5,600 installed. Fuel, venting, gas line and electrical work cause most of the spread, and we give a clear price before work starts.
Yes. Hazelwood publishes a winter design temperature of 2 degrees F. Most units have freeze protection that needs power, and exposed pipes still need insulation.
Often it does not. Tankless units draw more gas at once, so the pipe size is one of the first things we check.
Chloramines can wear rubber seals over time. They are not a reason to avoid tankless, but we check the rubber parts at service.
Questions about your situation? A licensed plumber is on the line any hour.
Call (855) 575-2890