To increase water pressure with a tankless water heater, ensure proper sizing, check for sediment buildup, install a pressure-boosting pump, and verify that all plumbing connections are secure and free of leaks.
Low water pressure from a tankless water heater can ruin showers and make daily tasks frustrating. While these systems provide endless hot water, they often struggle with pressure issues. This guide explains proven solutions to increase flow without sacrificing performance.
Why Tankless Heaters Cause Low Pressure
Tankless units heat water on demand by passing it through narrow heat exchanger pipes. This design creates more resistance than traditional tank heaters. Three main factors affect pressure:
- Heat exchanger design (more coils = more resistance)
- Mineral buildup in the unit
- Insufficient incoming water pressure
Minimum Pressure Requirements
Most tankless heaters need at least 40-50 psi to function properly. Gravity-fed systems (like roof tanks) often provide only 15-20 psi. Check your manual for exact specifications.
Effective Solutions to Increase Pressure
1. Install a Booster Pump
A water pressure pump before the heater solves low incoming pressure. Look for:
| Pump Type | Best For | Pressure Boost |
|---|---|---|
| Centrifugal | Whole house | 20-30 psi |
| Inline | Single fixtures | 10-15 psi |
For whole-house solutions, consider a recirculating pump system that maintains constant pressure.
2. Clean the Inlet Filter
Most tankless units have a mesh filter at the water inlet. Sediment buildup here restricts flow:
- Turn off water supply and power
- Locate filter (usually behind a cover plate)
- Remove and soak in vinegar for 30 minutes
- Rinse thoroughly before reinstalling
3. Adjust the Pressure Regulator
Many units have an adjustable pressure valve. Turn it clockwise to increase output pressure in small increments. Don’t exceed the manufacturer’s maximum setting.
4. Upgrade Pipe Size
Older homes often have 1/2″ pipes that restrict flow. Upgrading to 3/4″ pipes can double your water volume. This is especially helpful for parallel heater installations.
Advanced Solutions
Parallel Heater Installation
Adding a second unit splits the demand:
- Each heater serves separate zones (like different bathrooms)
- Maintains pressure when multiple fixtures run
- Requires proper sizing and professional installation
Point-of-Use Heaters
Small tankless units installed near high-demand fixtures eliminate long pipe runs that cause pressure drops. Ideal for:
- Remote bathrooms
- Kitchen sinks
- Laundry rooms
Maintenance for Optimal Pressure
Regular care prevents pressure loss:
- Annual descaling: Use a quality descaler to remove mineral deposits
- Filter cleaning: Check inlet filter every 3-6 months
- Pipe inspection: Look for corrosion or leaks that restrict flow
When to Call a Professional
Contact a plumber if you experience:
- Sudden pressure drops with no clear cause
- Visible leaks at the heater connections
- Error codes indicating flow problems
For complex installations like parallel systems or whole-house repiping, professional help ensures proper sizing and safety. The Rheem Tankless Water Heater Guide provides excellent technical specifications for planning upgrades.
