Skip to content
WaterHeaterCalc

Converting to tankless · Expert

Whole House Tankless Setup

Quick answer

At 199,000 BTU this is the largest residential gas input commonly sold, and the gas line is what stops units this size rather than the budget. A run that carries a 40,000 BTU tank will not carry this, so check the pipe before anything else on this page is ordered.

Who should not buy this: anyone whose gas line cannot carry roughly 193 cubic feet per hour over its real run length, which is most houses without an upgrade. That is not a hedge, it is the single most common reason a setup like this does not get installed as quoted.

Where it does fit, this is a house that genuinely runs three fixtures at once in a cold inlet region. Everything else on the list exists to keep a unit working that hard running for fifteen years.

The complete parts list

Every line below is a real listing with a live link. Prices come from verified catalog data and change often.

The unit

$1449.99

Check the gas line first. At this input the pipe is the project.

Gas and service

$89.45

Venting and condensate

$325.18

Recirculation, done with a timer rather than continuously

$375.97

A tankless unit and a recirculation loop interact: the loop keeps the unit cycling, which is exactly what a timer and a thermostat exist to limit.

Scale, which is what kills a hard working exchanger

$299.93

Control and containment

$317.34

Parts list total

$2857.86

15 lines across 6 groups. Prices change often and are a guide only. This is the parts list, not the installation: gas, flue and electrical work belong to the licensed trade that signs the permit.

Parts list

Get this parts list as a checklist

One email with the full list, every item linked, so you can tick it off at the supplier or on your phone.

No spam. Unsubscribe whenever you like.

What you can skip

Telling you not to buy something is what makes the rest of the list credible.

  • This list entirely, if the gas line cannot carry it. A starved burner is a carbon monoxide risk, not an inconvenience. Size the pipe first and let the answer decide the unit.
  • Recirculation, if the fixtures are close to the unit. It costs standing heat loss every hour it runs and buys nothing you notice.

What to upgrade first

  • The gas line, before anything else. It is the constraint, the largest cost, and the item most often missing from a quote.
  • Scale protection, in hard water. A unit running this hard scales faster than a lightly used one at the same hardness.

The other tiers in this ladder

  • Entry Gas Tankless Conversion (Beginner): The parts list for a first gas tankless installation, with the service valves, gas connector, venting and descaling kit
  • Condensing Gas Tankless Conversion (Intermediate): The condensing tankless setup with PVC venting, a condensate neutralizer, service valves, scale protection and the desca

The other way to do this

A like-for-like swap. The heater itself is often bought at a big box store with installation attached, and the accessory layer around it is where an online order genuinely makes sense.

Frequently asked questions

Who is the whole house tankless for?
Three bathroom houses with real simultaneous demand, and a gas line proven to carry the input. Everything on the list is either required in most jurisdictions or is the item that prevents the next failure, and the "what to skip" section says plainly what is not needed.
Do I need every item on this list?
No, and the page says which ones. The required group covers what most jurisdictions ask for on any water heater installation. Everything after it is a judgment call, and the skip section explains which items genuinely do not apply to a straightforward installation on a concrete floor near a drain.
Does this include the installation?
No. This is the parts list. Gas line, flue and electrical work belongs to the licensed trade that signs the permit, and what that work costs is a different question that HouseProjectCalc covers. Buying the parts yourself and having them fitted is common and usually cheaper than a supplied-and-fitted quote.
Are these prices current?
They come from verified catalog data and they move often, especially on accessories. Treat the total as a planning figure rather than a quote, and check each listing before ordering. Availability on water heater accessories moves even faster than price does.

This is a parts list, not an installation guide. A water heater is a pressure vessel: never cap, plug or remove the temperature and pressure relief valve, and the discharge pipe runs to within six inches of the floor with no valve and no upward run. Gas line, flue and vent work belongs to a licensed plumber or gas fitter, because improper venting produces carbon monoxide. Turn the breaker off before touching an element and never energise one that is not submerged. Water at 140 F scalds a child in seconds, which is what a thermostatic mixing valve exists to prevent.