How do you size a water heater for my house?
We size off how much hot water the house needs in its busiest hour, not off what’s in the closet now: bathrooms, how many people shower back to back, and whether the tub is standard or the deep soaker somebody added in a remodel.
Residential tanks come in 40, 50, and 75 gallon sizes, and the one in there now was chosen by whoever built the house — sometimes correctly. Bigger isn't automatically better. A 75-gallon tank in a two-person house reheats water nobody uses, every month, forever.
Tankless is sized by flow rate and temperature rise instead of volume, and we size it for January — incoming water is colder then, so a unit that keeps up all summer can disappoint you the first cold snap.
What does current code want on a replacement?
A short list of things that go wrong badly when they're missed, mostly the parts a handyman skips. Most of it is invisible once the closet door shuts, which is exactly why it gets skipped. Here's what current code wants on a replacement, and why.
| What code wants |
What it's for |
When it applies |
| Expansion tank |
Gives heated water room to expand instead of pushing against your fixtures and the relief valve |
Closed systems — any house with a PRV or backflow preventer at the meter |
| Drain pan and pan drain |
Catches a slow leak and routes it outside instead of through a ceiling |
Attics, second floors, anywhere above finished space |
| T&P discharge line |
Sends relief-valve discharge somewhere safe — full size, downhill, no threads on the end |
Every tank, no exceptions |
| Sediment trap on the gas line |
Catches scale and debris before it reaches the gas control valve |
Gas units |
| Vent sized and drafting |
Keeps combustion gases going up the flue instead of into the closet |
Atmospheric-vent gas units — we test the draft before we leave |
| Shutoff and dielectric connections |
Lets the unit be isolated, and keeps dissimilar metals from corroding at the nipples |
Every install |
Older Red Oak and Waxahachie houses are usually missing two: the expansion tank, because a pressure-reducing valve went in years after the heater and nobody revisited it, and the pan drain, cut and capped during some remodel. Both get corrected as part of the install.
Can you do it the same day?
Usually, if it's a standard tank swap and we can get to you. The common gas and electric sizes are the ones that fail most and stock best, and a like-for-like replacement is a 2–3 hour job.
When it isn’t same day, we’d rather say so on the phone: the unit has to be ordered, the closet needs modifying for a different footprint, the gas line is undersized, or you’re converting to tankless, a full-day job on its own. See tankless water heaters for what that involves.
The old heater goes with us either way, drained, disconnected and loaded. You are not left with a rusted tank in the side yard waiting on bulk trash day. Call (469) 505-8362 and describe what’s in the closet; that’s usually enough to tell you whether it’s a today job.
What does a water heater installation cost in Red Oak?
We quote it before we start, and it depends on more than the box. A firm price over the phone from someone who hasn't seen your closet is a guess, and the guess gets revised on arrival. Four things move the number:
- Tank or tankless, and what size
- Which code items the old install is missing — expansion tank, pan drain, a T&P line run somewhere it shouldn't be
- Where the unit lives. A garage is straightforward; an attic with a pull-down ladder is a different day.
- Whether the gas, water, or electrical has to be reworked to carry it