Tankless Water Heater Installation in Redmond: Sizing for Multiple Bathrooms

Planning tankless water heater installation in Redmond homeowners can rely on starts with one thing: realistic sizing for how many bathrooms you have and how your house actually uses hot water. A tankless unit can feel amazing when it is sized for your peak demand, but it can feel frustrating when two showers and a dishwasher push it past its limit.

This guide walks through tankless sizing in plain language, including a simple GPM tankless calculator approach you can do at home, how to think about 2 bath vs 3 bath tankless needs, and what to ask for in a tankless install quote Redmond so you can compare options confidently.

Tankless water heater installation in Redmond bathrooms

Bathroom count matters, but not as much as simultaneous use. A three-bath home where everyone showers at different times can need less capacity than a two-bath home with a busy morning rush.

2 bath vs 3 bath tankless: what changes

• Two-bath homes often hit peak demand when two showers run at once or when a shower overlaps with laundry.

• Three-bath homes are more likely to have overlapping showers, plus a dishwasher or a sink running, especially during mornings or evenings. In Redmond, the question is usually not “How many bathrooms do I have,” but “How often do we run two or three hot water tasks at the same time.”

Estimate your peak flow rate with a simple GPM tankless calculator

Tankless sizing is largely about peak flow rate, measured in gallons per minute (GPM), plus the temperature rise needed. The U.S. Department of Energy recommends estimating flow rate by measuring how much water a fixture delivers in one minute (a bucket test), then adding up fixtures you expect to run at the same time.

Step 1: List your “peak moment” fixtures

Pick the busiest realistic moment in your home. Common combinations:

• Shower + shower

• Shower + dishwasher

• Shower + laundry

• Shower + bathroom sink use

Step 2: Measure GPM (quick bucket test)

Use a 1-gallon container (or a bucket with markings), run the fixture at the normal setting, and time how long it takes to fill. Convert to GPM. This is the same basic approach DOE suggests for estimating flow rate if you do not know it.

Step 3: Add the GPM for simultaneous fixtures

That total is your target peak flow. If your peak is “two showers at once,” your tankless needs to keep up with that combined flow without temperature drop.

Do not ignore temperature rise in the Pacific Northwest

Tankless performance depends on both flow rate and how much the unit must heat the incoming water (temperature rise). DOE describes temperature rise as the difference between incoming water temperature and your desired hot water temperature, and notes that if you do not know incoming temperature, a common assumption is around 50°F.

In the Redmond area, incoming water can be cool enough that temperature rise becomes a real sizing factor. Higher temperature rise requires more heating capacity for the same flow rate.

Why this matters for multiple bathrooms

If your unit is sized only for GPM and not for temperature rise, you may notice:

• Hot water that cools down when another fixture turns on

• Reduced flow as the unit tries to maintain temperature

• “Warm, not hot” water during peak use

Gas vs electric tankless in Redmond: capacity and limitations

Both types can work, but they behave differently under load. DOE notes that tankless water heaters typically provide hot water at about 2–5 gallons per minute, and that gas models generally deliver higher flow rates than electric models. DOE also notes that even larger gas models can be stretched by simultaneous uses like a shower plus dishwasher.

When gas tankless is often a better fit

Gas tankless is commonly chosen when you need stronger multi-fixture performance, especially for multiple bathrooms. It is also more likely to handle higher peak demand without dropping temperature, assuming the gas line and venting support it.

When electric tankless can make sense

Electric tankless can work well for:

• Smaller homes with lighter simultaneous use

• Point-of-use applications (one bathroom, a remote sink)

• Homes where gas is not available For whole-home multi-bath demand, electric options often require careful planning around electrical service capacity.

What to ask for in a tankless install quote Redmond homeowners can compare

A good tankless install quote Redmond should tell you what the installer is actually building, not just what model they are hanging on the wall.

Sizing details you should see

• The expected peak GPM the unit is being sized to support

• How the installer accounted for temperature rise

• Whether the design is meant for simultaneous showers

Installation scope that affects real performance

• Gas line capacity (if gas): upgrades if needed

• Venting plan and materials

• Service valves for flushing and maintenance

• Condensate drain plan (for condensing units)

• Optional recirculation features if you want faster hot water delivery at distant fixtures A plumber Redmond homeowners trust should be able to explain these choices in plain language and show you how they match your household use.

Common sizing mistakes that lead to “tankless regret”

Sizing by bathrooms only

Bathroom count is a shortcut. Simultaneous usage is the truth.

Ignoring fixtures outside bathrooms

Dishwashers and laundry overlap are a common cause of temperature drop complaints.

Buying the cheapest unit instead of the right capacity

A lower-priced unit that cannot keep up becomes expensive in frustration and repeat service calls.

When to call a pro for safety

Call a professional right away if:

• You smell gas or suspect a gas leak

• You need new venting or changes to existing venting

• You are unsure whether your gas line can support a higher-BTU appliance

• You are not confident about electrical service capacity for an electric tankless

• You want assurance the unit is sized correctly for multi-bath simultaneous use Tankless installation involves gas, venting, electricity, pressure, and very hot water. A pro can keep the project safe and code-compliant.

FAQ

What size tankless do I need for 2 bath vs 3 bath tankless use?

It depends on how often you run fixtures at the same time. The key is your peak GPM plus temperature rise, not just bathroom count.

What is a GPM tankless calculator and why does it matter?

It is a way to estimate peak flow by measuring fixture flow rates and adding the ones you expect to run simultaneously. This helps prevent undersizing.

Why do some tankless systems struggle with multiple showers?

If simultaneous demand exceeds the unit’s capacity, temperature can drop or flow can reduce. DOE notes tankless units can be stretched by multiple simultaneous uses.

What should be included in a tankless install quote Redmond homeowners request?

Sizing assumptions, gas line or electrical scope, venting plan, service valves for flushing, and any code or connection upgrades.

Should I hire a plumber in Redmond homeowners recommend for tankless installs?

Yes, especially for multi-bath homes. Correct sizing and safe venting or electrical work are what make the system feel “worth it.”

The best tankless water heater installation in Redmond plan starts with how your household uses hot water during the busiest hour. Measure your peak flow, account for temperature rise, and make sure your quote includes the installation details that affect performance.

Not sure what size you need? Schedule a sizing assessment with American Mains and Drains so your system fits your home’s actual hot water use.

Schedule service or request an inspection today at: https://www.americanmainsanddrains.com/