How many GPM do I actually need for my house?
Here's the honest answer: add up the GPM of the fixtures you might use simultaneously. A typical shower runs 2.0-2.5 GPM. A kitchen sink runs 1.5-2.0 GPM. A dishwasher draws 1.5 GPM during fills. So a 3-bathroom home that might run two showers plus a kitchen sink needs around 6-7 GPM. Add a margin and you're at 8 GPM. For most 3-4 bath homes in our area, a 199K BTU condensing tankless (8-11 GPM at Texas ground water temps) handles it. For 5+ bathroom homes we sometimes spec dual-unit installs.
Why does Texas ground water temperature matter?
Because tankless GPM is rated at a specific temperature rise. If your incoming water is 50°F and you want 120°F output, that's a 70° rise. Same unit at our Texas ground water of 65-70°F only needs a 50-55° rise to hit 120°F. The math: less rise = more GPM at the tap. A 199K BTU unit rated at 9 GPM with a 70° rise can hit closer to 11 GPM in our climate. Tankless was built for warm climates - we just happen to live in one.
What's "condensing" vs "non-condensing" and which should I buy?
A condensing tankless extracts an extra round of heat from its own exhaust before venting it out, which is why condensing units hit 0.96+ UEF vs 0.82-0.86 for non-condensing. The exhaust is cool enough that condensing units vent through 2-3 inch PVC pipe - cheap, easy to route. Non-condensing units need stainless steel venting because the exhaust is hot. For most new installs we recommend condensing - the efficiency pays for itself and PVC venting opens up more install locations.
Can I install a tankless myself to save money?
Texas requires a licensed plumber for gas connections and a permit for water heater replacements - so legally, no, not on a gas tankless. Beyond the legal side: gas line sizing errors cause hard-to-trace performance issues, venting errors cause CO leaks, and improper condensate drainage causes premature heat exchanger failure. Manufacturer warranties on most tankless brands require licensed installation - so a DIY install voids your 12-15 year heat exchanger warranty. For an electric tankless point-of-use install, it's more accessible but still requires a permit. We'll always tell you when an install is straightforward enough that you could legitimately DIY it.
Does a tankless really need maintenance every year?
Yes, and not optional in Central Texas. Our water hardness puts mineral scale on the heat exchanger every time the unit fires. Scale buildup reduces efficiency, increases the chance of error codes, and eventually kills the heat exchanger. Annual descaling - we flush vinegar or descaling solution through the unit for 45 minutes - keeps it running like new. Skip it for 5 years and you may need a heat exchanger replacement; do it every year and the unit lasts 20+. Our maintenance plan includes the annual flush.
Should I add a recirculation pump?
If your fixtures are more than 30-40 feet from the water heater, yes - or you'll wait 20+ seconds for hot water at the far fixture every time. Two approaches: (1) An add-on recirc pump on a dedicated return line - cleanest option, requires plumbing. (2) Built-in recirculation on units like the Navien NPE-A2 or Rinnai RUR199iN - simpler if you don't have a return line. Both work; choice depends on plumbing layout and budget. We talk through it during the quote.
Can I run a tankless during a Texas freeze without power?
No - and this matters during winter storms. Gas tankless units need electricity for the ignition, fan, and controls. A power outage means no hot water until power's back. Worse: tankless units can freeze in extended outages if they lose power during a hard freeze, which can crack the heat exchanger. What helps: outdoor-mounted units have freeze-protection heaters that draw very little power and can run off a small backup; some homeowners with tankless add a small generator or large battery backup specifically for the unit. If freeze events are a concern for you, we'll talk options at the quote.
How long does a tankless installation actually take?
A tank-to-tankless conversion typically takes 6-9 hours - longer than a like-for-like tank swap because of the gas line upsize, new venting, electrical, and condensate work. We try to start in the morning and finish the same day on most jobs. A direct tankless-to-tankless replacement is faster, usually 4-5 hours. The first install is the long one; future replacements (in 20 years) will be quick because the infrastructure is already there.