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Plumbing · Water heaters

Tankless install or conversion

A tankless unit installed properly: the gas line sized for it, the venting run to spec, the condensate handled, and isolation valves so it can be serviced.

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One flat fee to find out what is wrong. You are told it on the phone before anyone is dispatched, and it comes off the job if you hire us. Read our Plain Terms

A wall-mounted tankless water heater on a stucco exterior wall with copper hot and cold lines, red and blue isolation valves, a yellow corrugated gas connector with its own shutoff, a condensate drain and a weatherproof electrical disconnect
An exterior tankless with isolation valves, so it can be descaled without cutting anything. Southern California.

What the work is

A tankless heater draws far more gas at peak than a tank does, so the existing line is often too small. Undersized gas is the single most common fault we find on a tankless that someone else installed, and it shows up as a unit that cannot hold temperature when two fixtures run.

The rest of a correct install is venting to the manufacturer's spec, condensate routed to a legal termination on a condensing unit, and a pair of isolation valves so the heat exchanger can be flushed without cutting pipe.

The isolation valves are not optional here. On this water, a tankless has to be descaled, and a unit installed without them costs more every single time.

What is included

  • The unit, mounted, connected and commissioned to the manufacturer's start-up procedure
  • Gas line sizing, and upsizing where the calculation requires it
  • Venting to the manufacturer's specification
  • Condensate routing on a condensing unit
  • Isolation service valves on both sides
  • The permit and the inspection
  • Hauling the old heater away

What is not

  • Treating the water. Priced separately, and read the note below before you decide against it
  • Electrical beyond a like-for-like connection
  • Structural work to carry the unit or the vent
  • Any promise the warranty will pay out on an untreated install

Hardness, and what the warranties actually say

St. George's Water Distribution Division tells residents to set a softener to 18 grains per gallon, with a maximum of 22. Four tankless makers cap total hardness at 200 mg/L, which is about 12 grains. That gap is the single most important fact about water heaters in this county, and it is the reason the guide below exists.

Read the exclusions carefully rather than taking anyone's summary of them, including ours. They are not all the same kind of clause: some exclude the damage, one voids the warranty. One maker publishes no hardness figure at all and expressly covers heat exchanger failure from scale on certain units. That is why the guide below quotes the documents instead of paraphrasing them.

The practical version: an untreated tankless in St. George is an uninsured heat exchanger. Softened water leaving a properly set softener is functionally zero to one grain, which clears every limit in the table.

What to ask anyone quoting this, us included

  • What gas line size does this unit need at full fire, and what have I got?
  • Are isolation valves included?
  • Which warranty applies, and what does it say about hardness?
  • Where does the condensate go?

What we can show you in writing

Every line traces to a document we read in full. The number after a sentence points to the research below.

  • The City of St. George's Water Distribution Division instructs residents to set water softeners to 18 grains per gallon, with a maximum of 22 grains.1
  • A.O. Smith's gas tankless warranty excludes damage from hard water over 7 grains per gallon in a single-family home. St. George runs 18 to 22.2
  • Noritz voids outright above 12 grains per gallon.2
  • Rinnai's manual states it flatly, and separately tells you a hard-water area needs treatment and more frequent flushing.2
  • Rheem excludes heat exchanger failures caused by scale, and Navien excludes damage from hard water deposits and mineral build-up.2
  • Rinnai and Rheem also void on hours, not just years: both stop at 12,000 operating hours, whichever comes first. A scaled unit runs longer per gallon delivered, so hard water spends that clock faster too.2
2 more facts, with sources
  • These are exclusions on the damage, not a blanket void of the whole warranty. A manufacturer denies a scale-related heat exchanger claim; it does not normally void an unrelated control board failure.2
  • Softening is what clears the limits. Softened output runs about 0 to 1 grain per gallon, under every threshold above. The 18-grain figure is what you tell the softener is coming in, not what comes out of it.2

Where this comes from

Every line above traces to a document we read in full. The number after a sentence points to the research below; hover it for the section. If you find a line wrong, tell us and we will fix it and say so.

  1. Environment, water and ground research, August 2026 Compiled from the cities' own water quality reports, Utah Geological Survey Special Study 127, the Utah State Hazard Mitigation Plan, Washington County GIS hazard layers, NOAA climate records, EPA radon zones and Census QuickFacts. 1 section cited. Hover a number above for the section.
  2. Plumbing research, August 2026 Compiled from manufacturer warranty documents and installation manuals (A.O. Smith, Noritz, Rinnai, Rheem, Navien, Bradford White), the Battelle / Water Quality Research Foundation study, the Utah Code and DOPL rules. 4 sections cited. Hover a number above for the section.

This work

What it looks like on the job.

Southern California work by the same crew. Every caption names the city.

  • A wall-mounted condensing tankless water heater with its gas, water and venting connections made up
    A condensing tankless, installed. Manhattan Beach, California.
  • A new gas line run in black iron with code-compliant fittings and a shutoff at the appliance
    A permitted gas line to an outdoor fire pit. Rolling Hills Estates, California.
  • A wall-mounted tankless water heater on an exterior wall, with the gas and water connections made up and tools still on the bench below
    An exterior tankless, part way through commissioning. Southern California.
  • A tankless water heater mounted in a tiled interior closet with its venting and a yellow gas connector below
    A tankless in an interior closet. Southern California.

Read before you decide

The rest of water heaters

The quote is the number. There is no second number.

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