Whole house filters are one of the fastest-growing jobs we supply. The filter itself is the easy part to choose. What makes the job quick or painful is the fit-off: the valves, the bypass, the thread adaptors and the one fitting nobody remembered until the water was off. This guide walks through a standard fit-off on a 20mm copper main using our Water Filtration Installation Kit, and applies to both systems we sell: the Bluegum Triple Stage Filter & Softener ($999) and the VIVA Triple Stage system ($1,999).
Why the bypass matters
Cartridges get changed every 6 to 12 months. Without a bypass, every change means shutting the house off at the meter. With one, you close two valves, open a third, and the house keeps running on unfiltered water while the housings are open. It also lets you keep water on if a housing O-ring fails, and isolate the filter completely if the owner ever removes it. On a job you'll be called back to service, the bypass pays for itself on the first visit.
The three-valve layout
A standard bypass uses two tees on the main and three valves:
- Inlet tee on the main after the meter. The branch runs to the filter inlet through valve A (normally open).
- Outlet tee further along the main. The branch comes back from the filter outlet through valve B (normally open).
- Valve C sits on the main between the two tees (normally closed) and is the bypass.
In service, A and B are open and C is closed, so everything goes through the filter. To change cartridges: close A and B, open C. Tag valve C “BYPASS — NORMALLY CLOSED” so the next person doesn't leave the house running on unfiltered water.
What's in the kit and where each part goes
The kit ($99) is built around this layout in 20mm, all lead free DR brass and press fittings:
| Qty | Fitting | Where it goes |
|---|---|---|
| 2 | 20mm press water tees | Inlet and outlet tees on the main |
| 1 | 20mm press x press ball valve | Valve C, the bypass on the main |
| 1 | 20mm press x MI ball valve | Valve A or B on a filter branch |
| 1 | 20mm press x FI ball valve | Valve A or B on the other filter branch |
| 2 | 20mm M/F elbows | Turning the branches into the filter ports |
| 2 | 25mm x 20mm reducing nipples | Taking the 25mm (1”) filter ports down to 20mm |
| 1 | 20mm dual check valve | Backflow protection (see below) |
Copper pipe isn't included. Both valves on the filter branches are press one end and threaded the other, which is what lets you go from copper straight onto the filter's threaded connections without silver-brazing next to plastic housings. If you're new to press on water services, our press vs brazing cost comparison and press ball valve guide cover the basics.
Check the thread before you cut in
This is the step that catches people. The Bluegum unit's inlet and outlet are listed as 1” NPT brass connections (CW511, AS 3688), and it comes with two brass connectors. NPT and BSP threads look alike but don't seal against each other. Before you start, confirm what thread the filter presents at the point you're connecting to and that it matches the BSP fittings you're running into it, using the connectors supplied with the filter where they convert. The VIVA listing describes heavy-duty brass connectors with double O-rings; check their thread on the unit before cutting the main too.
Check the pressure
The VIVA system is rated for 0.1–0.6 MPa (100–600 kPa) and 5–35°C. Plenty of mains supplies sit above that, especially on low-lying streets and new estates. Measure static pressure at the meter. If it's high, fit a pressure reducing valve upstream of the filter; our RBM Rinox PRV comparison covers the options. The Bluegum listing gives gauges reading 0–1.6 MPa but no separate working pressure figure, so check the installation instructions supplied with the unit for its limit. Filters are cold-water only: they go on the main before the hot water system, never on a hot line.
The dual check valve
A dual check valve stops water held in the filter from backing up into the supply. Many water authorities fit one at the meter already, and local requirements vary. Check what's at the meter and what your authority wants before deciding whether to fit the kit's DCV on the filter inlet side or keep it for the next job. Our dual check valve guide covers the backflow ratings.
Sizing: is 20mm enough?
Most houses run a 20mm main, and the kit is 20mm throughout. The Bluegum unit is listed for flow up to 40 L/min and the VIVA at 50–60 L/min, both through full-size 20” x 4.5” housings. If the property is on a 25mm service or you're feeding a large house with high simultaneous demand, carry 25mm through the bypass instead and don't neck the main down to 20mm just to suit the kit.
Commissioning
- With valves A and B closed and C open, finish and press all joints.
- Fit the cartridges, open A slowly, bleed air at the housings, then open B and close C.
- Run a tap downstream until it runs clear, then check every joint and housing for weeps.
- Note the starting reading on each housing gauge (on the Bluegum) so the owner can tell when a cartridge is loading up.
For what each system removes and the cartridge schedule, see the Bluegum whole house filter guide and what triple-stage systems actually remove.
Frequently Asked Questions
Do I need a bypass on a whole house filter?
It isn't mandatory everywhere, but without one every cartridge change means shutting the whole house off at the meter. Two tees and three valves let the house run on unfiltered water while the filter is serviced.
What size fittings do I need?
For a standard 20mm house main, 20mm throughout. Our installation kit includes two 20mm press tees, three 20mm ball valves, two elbows, two 25mm x 20mm reducing nipples for the 1” filter ports, and a dual check valve. Copper pipe is extra.
Can a whole house filter go on the hot water line?
No. Install it on the cold main before the hot water system, so the hot water system is fed filtered water. The VIVA unit is rated to 35°C.
What if my mains pressure is high?
Measure static pressure at the meter. If it exceeds the filter's rating (600 kPa on the VIVA), fit a pressure reducing valve upstream of the filter.