Buying a new water heater: how to choose the size, the type, and the install

Replacing a water heater on your own schedule, rather than the morning it floods the garage, means you actually get to choose the right unit instead of taking whatever is on the truck. That is a real advantage, and it is worth using well. The choice has three parts: the size, the type, and the quality of the installation itself. Getting all three right is the difference between a heater that quietly lasts and one that disappoints or fails early. This is how to think through each part for a San Tan Valley home.

Size: match the household, not the box

The most common sizing mistakes are in both directions. An undersized heater runs out of hot water mid-shower; a wildly oversized one wastes money keeping water hot that nobody uses. The right size is matched to how many people live in the home and how the hot water actually gets used, not to whatever is on sale. For most local homes, a right-sized tank in the 40 to 50 gallon range covers a typical household comfortably. A larger household, or a home with a big soaking tub and several fixtures that run at once, may justify a larger tank or a different type entirely. The point is to size to your real usage, which is a short conversation, rather than defaulting to the biggest unit that fits.

Type: tank or tankless, honestly

The tank-versus-tankless question gets oversimplified, so here is the honest version for this water. A standard tank is simple, forgiving, and cheaper up front, and its main maintenance need here is an annual flush. A tankless unit gives endless hot water and takes up far less space, with no stored tank to fail across a floor, but on 16 to 20 grain water it will scale up faster and genuinely needs a softener ahead of it plus periodic descaling to deliver on its promise. Neither is the right answer for everyone. If you will keep up the maintenance, tankless is excellent; if you want the lowest-fuss option, a well-installed tank is the more honest pick. The tankless page goes deeper on that tradeoff.

The install details a cheap quote skips

These are the parts that do not show up on day one but decide whether the heater lasts and passes inspection.

• An expansion tank, required on closed systems and genuinely needed here
• A new temperature and pressure relief valve with a correct drain line
• A sediment trap on the gas connection and a proper seismic strap
• Dielectric unions to slow the corrosion hard water accelerates
• New flex connectors and a shutoff you can actually reach

None of these is glamorous, and every one of them is skippable to shave a quote. Each one skipped shows up later as a callback, an inspection problem, or a shortened life on the new unit.

The hard-water decision that comes with it

Whatever unit you choose, its worst enemy is the same mineral load that killed the last one, so the single best companion decision is a water softener. Installed alongside a new heater, it is what actually lets the unit reach its rated life instead of scaling toward an early grave. This is doubly true for tankless, where softened water is close to mandatory. Thinking of the heater and the water treatment as one decision, rather than two, is how San Tan Valley homeowners avoid replacing appliances on the short cycle that hard water otherwise imposes.

If you are switching to gas or tankless, plan the fuel

One practical detail that trips up upgrades: a tankless heater draws considerably more gas at once than a standard tank, so an existing gas line sized for the old tank may not feed a new tankless unit properly. Part of planning a tankless install, or any switch that increases gas demand, is confirming the gas line and meter can supply it and upsizing the line if they cannot, which is where the gas line work comes in. Sorting that out before the unit is ordered avoids the disappointment of a new tankless heater that cannot perform because it is starved for gas.

The bottom line

A good water heater choice is three decisions made together: a size matched to your actual usage, a type that fits how much maintenance you want to do on this water, and an installation that includes the unglamorous parts a cheap quote leaves out. Pair whatever you choose with a softener, and if you are moving to tankless, plan the gas supply first. Made on your schedule, all of this is a calm conversation; made during a flood, it is whatever is available. The installation page covers how the day itself runs.

Common questions