A correctly sized whole house water filter causes only a small pressure drop that most people don't notice. Problems come from undersized housings, small ports or a clogged sediment cartridge. Sizing the system to your home's peak flow and changing cartridges on schedule keeps pressure where it should be.
- Size to peak flow, not average use.
- 20-inch housings and 1-inch ports keep flow high.
- A blocked sediment cartridge is the most common cause of pressure loss.
What affects pressure?
| Factor | Why it matters |
|---|---|
| Housing size | Larger (20-inch, 4.5-inch wide) cartridges flow more freely |
| Port size | Matching your pipe (often 20–25 mm) avoids a bottleneck |
| Cartridge age | Sediment cartridges clog over time |
| Number of stages | Each stage adds a little resistance |
How much water does a home use at once?
A water-efficient shower uses up to 9 litres a minute under the WELS rating scheme. Two showers, a washing machine and a kitchen tap running together is the peak a system has to handle. We measure your flow at the Home Water Check and size the housings to it.
What if pressure drops later?
Check the sediment cartridge first. If it's brown and caked, it's done its job and needs changing. The Care Plan changes it on schedule and photographs the old one so you can see what it caught. See maintenance.
Questions
Why did my water pressure drop after installing a filter?
Usually an undersized system or a clogged sediment cartridge. A correctly sized system with a fresh cartridge has very little effect.
Can a bypass valve help?
Yes. It lets you bypass the filter temporarily if a cartridge is blocked, until it's replaced.
Written by the Whole Home Water team and reviewed against the Australian Drinking Water Guidelines. General information only; your Home Water Check gives advice for your home.
Plumbing and installation details reviewed by a licensed plumber. See our editorial policy.