A whole house water filter diagram is mostly about order and about valves. Order, because the stages have to be sequenced so each protects the next. Valves, because the difference between a system you can service in ten minutes and one that requires shutting off the whole property is three fittings that cost very little at installation and are impossible to add cheaply afterwards.
Where it sits on the incoming main
The filter goes on the main after the meter and the main shutoff, before anything branches off, so that every outlet in the property is served by treated water. Critically it goes before the water heater, since a heater fed with untreated water scales and stains from the inside and no filter downstream recovers that. The one branch usually taken ahead of the filter is the outside tap for irrigation, since watering the garden through a cartridge simply consumes it for no benefit.
The order of the stages
Coarse to fine, then chemical, then anything biological. Sediment first, because grit damages everything after it, with a backwashing tank or a centrifugal separator ahead of the cartridges on genuinely dirty supplies. Carbon second, removing chlorine before it reaches softener resin, which it degrades over time. Softener third, since it needs both clean and dechlorinated water to last. Ultraviolet last of all, immediately before distribution, because it only works on water that everything upstream has already made clear.
The valves the diagram must show
An isolation valve either side of each filter housing, so a cartridge change does not mean shutting the property down. A bypass loop around the whole assembly, so the house still has water during a service or a failure, which matters most in the properties where nobody can go without. A pressure gauge before and after the filter bank, which is the only honest way to know when a cartridge is spent rather than guessing on a calendar. And a drain connection for anything that backwashes.
Clearances and mounting
Diagrams show the pipework and leave out the space, which is what defeats installations in practice. Leave clearance below each housing equal to the sump depth or the cartridge cannot be withdrawn without cutting pipework. Mount the housings on brackets to a solid surface rather than supporting them on the plumbing, since a full big diameter sump is heavy. Keep the assembly somewhere that will not freeze and where a leak can drain safely. Our whole house filter installation guide covers the pipework runs in detail.
Questions people ask about whole house water filter diagram
Where on the main does a whole house filter go?
After the meter and main shutoff, before any branches, and always before the water heater so the heater is fed treated water.
What order do the stages go in?
Sediment, then carbon, then softener, then ultraviolet last. Each stage protects the one after it, and UV needs clear water to work.
Which valves should I fit?
Isolation valves either side of each housing, a bypass loop around the whole assembly, and pressure gauges before and after the bank.
Should the outside tap be filtered?
Usually not. Branching irrigation off ahead of the filter avoids consuming cartridge capacity on water going onto the garden.