Tankless water heater conversion is one of the most over-sold home renovations in BC. The marketing talks about endless hot water, smaller footprint, and lower energy bills — all true. What the marketing doesn't talk about: gas line sizing, venting requirements, permit complexity, and a total install cost that often runs 2.5–3× a comparable tank replacement. We're not anti-tankless — done in the right home, it's a great long-term investment. But the customers who regret it are the ones who didn't get an honest scope before committing. Here's the full picture.
What a 'simple' tankless conversion really involves
Replacing a tank water heater with a tankless on the same wall, same fuel, same approximate location seems like a straightforward swap. In practice, six things usually need attention:
1. Gas line sizing
A typical residential gas tank runs at 35,000–50,000 BTU input. A whole-home gas tankless runs at 150,000–199,000 BTU input — 3–4× the demand on the gas supply. Most BC homes built before 2010 have a 1/2-inch gas line to the water heater, which is sized for the tank but undersized for tankless. Upsize to 3/4-inch is required for almost every tankless install we do, often back to the gas meter. This single requirement adds significant cost.
2. Venting
Tank water heaters typically vent through a B-vent (round metal pipe) up through the roof, drawing combustion air from inside the house. Modern condensing tankless units use direct-vent (PVC or polypropylene pipe) through an exterior wall, drawing combustion air from outside via a concentric or twin-pipe system. The venting type is fundamentally different — you can't reuse the existing B-vent. Routing the new vent to an acceptable termination location may require running it through a wall, soffit, or roof.
3. Combustion air provision
BC building code requires specific provisions for combustion air on every gas appliance. Tankless units, when direct-vented properly, pull combustion air from outside through the dedicated intake. But the installation needs to verify the surrounding area meets requirements — particularly important when the new tankless is being installed in a closet or small mechanical room.
4. Electrical
Gas tankless units need a 120V electrical outlet within reach of the unit — usually a dedicated 15-amp circuit. The existing water heater location may not have one. Adding the circuit means an electrician on site (or our crew if licensed) and a small bump in the project scope.
5. Condensate drainage
Modern condensing tankless units produce a small amount of acidic condensate (a byproduct of the high-efficiency combustion process). This needs to drain — either to a nearby floor drain, a condensate pump that lifts it to a higher drain point, or through a neutralization cartridge first if discharging into a metal pipe. Code-required, manufacturer-specified, often overlooked on quick-quote estimates.
6. Permit and inspection
Tank-to-tankless conversion triggers both a plumbing permit and a gas permit in every Lower Mainland municipality. The work requires a BC-licensed gas fitter (mandatory for any gas connection or alteration), the rough-in is inspected before final connection, and final inspection covers all of the above. Permit work adds time — the install itself may take 1 day but coordinating inspections may extend the project timeline.
Real-world install timelines
- Best case: straightforward tank-to-tankless, gas line already 3/4 inch, vent path through accessible exterior wall, existing 120V outlet within reach, floor drain present — 6–8 hours, 1 day on site
- Typical case: gas line upsize from 1/2 to 3/4 inch back to meter, new vent through wall, new 120V circuit, condensate pump — 1.5–2 days
- Complex case: tankless in a new location (relocation), full gas line replumb, new vent routing through finished space — 3 days, plus drywall repair after
We give a realistic timeline at quote, not at install. If we discover something on site that changes the scope, we stop and re-quote — not just push through and bill higher.
Real-world costs — order of magnitude
We don't post fixed pricing because every home is different, but to give honest order-of-magnitude context:
- Comparable gas tank replacement (40 or 50 gallon, like-for-like): smaller job, fits in a few hours
- Gas tankless conversion with simple scope (everything already in place): mid-range project
- Gas tankless conversion with typical BC home scope (gas line upsize, vent through wall, condensate handling): significantly more — usually 2.5–3× the tank replacement cost
- Gas tankless conversion with complex scope (relocation, finished-wall vent path, electrical work): the most expensive scenario
On a 20-year cost basis the math often favours tankless even at the higher install cost — but the upfront capital matters and homeowners deserve to know the real number, not a low-ball quote that gets revised on day-one of install.
Brands we install most often
Three brands cover almost all our BC tankless installs:
Navien
Korean manufacturer, the dominant tankless brand in the Lower Mainland. Excellent condensing efficiency, good cold-climate performance, solid warranty (15 years on the heat exchanger, common units). Our default recommendation for most BC homes.
Rinnai
Japanese manufacturer, very reliable, slightly less feature-rich than Navien at comparable price points. Strong dealer network. Good choice when local parts availability matters.
Noritz
Premium positioning, very good build quality, slightly higher cost. Strong on specific use cases (high-flow simultaneous demand, very low minimum flow rates).
Other brands we sometimes install when specifically requested: Rheem, Bosch. We avoid the budget tankless brands sold on Amazon — service availability and parts in BC are unreliable.
Sizing for BC water temperature
Critical and frequently miscalculated. BC's incoming water temperature drops to ~7°C in winter and rises to ~13°C in summer. Tankless capacity ratings are typically given at a temperature rise of 35°F (~20°C in metric). In BC winter, a 49°C (120°F) shower delivered from 7°C incoming water requires a 42°C rise — well above the spec-sheet rating. Real-world capacity is meaningfully lower than the showroom number.
Practical sizing for whole-house Lower Mainland tankless:
- 1–2 bathrooms, 2–3 people: 160,000–180,000 BTU unit
- 2–3 bathrooms, family of 4: 180,000–199,000 BTU unit
- 3+ bathrooms, 5+ people: 199,000 BTU single unit, OR cascade two units in parallel
Maintenance — required, not optional
Tankless units require annual descaling to maintain manufacturer warranty in most BC water conditions. This is a flush of the heat exchanger with a mild acid (commonly white vinegar) to remove mineral build-up that accumulates over a year of operation. The process takes ~90 minutes and costs $150–300 as a service call. Skipping it voids warranty in many cases AND meaningfully shortens unit life.
Some homeowners DIY the descaling — viable if you're comfortable with isolating the unit, connecting a circulation pump, and handling the descaling solution. We offer it as an annual service for customers who prefer to have it handled.
When NOT to convert to tankless
Honest counter-cases:
- Short-stay home (selling in <5 years) — payback period exceeds your ownership horizon
- Vacation home with intermittent use — standby losses of a tank don't apply when nobody's home, so the tankless advantage shrinks
- Very small household, 1 person — tank standby losses are smaller percentage of total energy use
- No gas service, electrical panel can't support a tankless electric — sometimes the right answer is just replacing the existing tank
- Tight budget — a tank replacement now plus saving for tankless in 5 years can be the financially smarter sequence
Frequently asked
Will the install pay for itself in energy savings?
Depends on your household. Heavy hot-water households see real annual savings; light households see smaller savings. The payback period is typically 7–12 years for most BC homes. Add the longer service life (18–20 years vs 8–12) and the total lifetime cost picture often favours tankless.
Can I have hot water during install?
No — there's a window of typically 4–6 hours where neither the old tank nor the new tankless is operational. We schedule installs to minimize disruption and complete in one day where possible. If you need overnight hot water during a multi-day install, we make sure the old unit is left functional until the new one is fully connected.
Do you handle the permits?
Yes — both plumbing and gas permits, plus all inspections, are handled by us. You don't talk to the city. You get the completed paperwork at handover.
Got the problem we just described? We answer 24/7 across Surrey, Langley, Vancouver, Burnaby, Coquitlam, Delta, White Rock, and Richmond. Call Mr. Plunger Plumbing & Drainage at (604) 870-1442 — real plumber on the line, exact ETA before dispatch, up-front quote before any work starts.