DIY Whole House Water Filtration: Step-by-Step Guide: Fast-Track Guide to Installing Your Own Whole Home Water Filter

I’ve installed and maintained several whole-house filtration systems over the past decade, and the same pattern shows up every time: clear upfront planning makes the mechanical work straightforward. A whole-house (point-of-entry) filter treats all incoming water, protecting fixtures, appliances, and skin from sediment, chlorine byproducts, and scale. Before you open a single valve, get real about water quality and flow demand—those two variables dictate everything from cartridge type to plumbing size. Steelcase’s research has shown water and indoor environmental quality shape comfort and health perceptions at home and work, and WELL v2 includes dedicated Water features (W01–W08) focused on quality, sediment, and residual disinfectants—use those baselines to define your target performance.

Flow must match your home’s peak demand. A typical single-family home with 2–3 bathrooms often sees 6–12 gpm during simultaneous showering and appliance use, while larger homes may hit 12–20 gpm. Many 10-inch large-diameter ("big blue") housings drop around 2–5 psi at 10 gpm depending on media and micron rating; stack too many stages and you’ll feel it in the shower. WELL v2’s Water concept emphasizes maintaining disinfectant management without unacceptable byproducts—if you plan to reduce chlorine taste with carbon, make sure you don’t unintentionally promote microbial growth by neglecting change-out intervals. For a practical overview of water criteria from a health-and-comfort framework, the WELL v2 resource is a solid touchpoint.

Understand Your Water: Test, Then Specify

Start by pulling a comprehensive water test. If you’re on municipal supply, ask your utility for the Consumer Confidence Report and supplement with an at-home kit or third-party lab test to capture free chlorine/chloramine, pH, hardness (grains per gallon), iron, manganese, turbidity, and total dissolved solids (TDS). For private wells, lab testing is essential—screen for bacteria (total coliform/E. coli), nitrate/nitrite, iron, manganese, hydrogen sulfide, and hardness. Your filtration stack depends on these results: sediment first, then chemical reduction (often carbon), then specialty media (iron/sulfur/scale) as needed, and disinfection where required.

Sizing the System: Flow, Pressure, and Pipe Diameters

- Measure static pressure (house off) and dynamic pressure (fixtures running). Most homes sit between 40–70 psi. Avoid dropping below ~35 psi at points of use.

- Match housing size to demand: 4.5" x 10" housings are fine for small loads; 4.5" x 20" reduce pressure drop at higher flows.

- Keep pipe size consistent with your main: 3/4" for small homes, 1" for larger. Undersizing is the fastest route to pressure complaints.

- Check pressure drop tables for your chosen cartridges. High-micron sediment (20–50 µm) up front protects finer media without choking flow.

Choose Your Filtration Stack

- Stage 1: Sediment filter (pleated or spun polypropylene). Typical 20–5 µm. Pleated is washable and offers lower pressure drop; spun is low cost and disposable.

- Stage 2: Carbon block or catalytic carbon for taste/odor and chlorine/chloramine reduction. Catalytic carbon handles chloramine better; confirm manufacturer data and change-out capacity.

- Specialty Media (as needed): Iron/manganese filters (air-injection oxidizing filter or greensand with oxidant), KDF for heavy metals/chlorine support, or a scale-control cartridge (template-assisted crystallization) when a softener is not desired.

- Disinfection: UV at point-of-entry for well water or when microbiological risk exists. UV requires prefiltration to low turbidity and proper flow sizing.

Placement in the House

Install the system right after the main shutoff and pressure regulator (if present), before the water heater to protect hot and cold lines. Branch off an untreated outdoor hose bib if desired—no reason to spend carbon capacity on irrigation. If you’re mapping a utility room remodel or a mechanical-wall rework, pre-visualize clearances for sump removal, bypass access, and drain routing. When I plan compact mechanical rooms, I sketch the water path and maintenance swing spaces first to avoid knuckle-busting later.

Tools and Materials

- Filter housings with mounting brackets (4.5" x 20" recommended for family homes seeking low pressure drop).

- Cartridges: sediment and carbon as specified; specialty media as required.

- Bypass manifold: three ball valves (inlet, bypass, outlet).

- Unions or SharkBite-style fittings for serviceability (use copper/PEX adaptors as needed).

- Pressure gauges (before and after the bank) to monitor pressure drop and service intervals.

- Pipe: copper L or PEX-A/B, plus fittings, Teflon tape, pipe cutter, deburring tool, crimp or press tools, or solder kit if sweating copper.

- UV unit and electrical outlet if using disinfection.

- Sump wrench, bucket, towels, and food-grade silicone grease for O-rings.

- Mounting board (plywood) anchored to studs for a clean, rigid assembly.

Step-by-Step Installation

1) Plan and Depressurize

- Photograph the main, note shutoff orientation, heater location, and space.

- Mark the filter location allowing at least 4–6 inches below housings for cartridge changes.

- Shut off the main and open a low fixture (e.g., basement hose bib) to drain pressure.

2) Cut and Prep the Main

- Cut the cold main line after the shutoff and regulator. Deburr copper; square-cut PEX.

- Dry fit your bypass manifold: inlet valve, bypass valve, outlet valve forming a capital “H.” Include unions for easy removal.

- Mount a plywood backer and secure brackets into studs.

3) Install Housings and Gauges

- Pipe from inlet valve to Stage 1 housing, then daisy-chain to Stage 2 and any specialty stages. Keep flow arrows aligned.

- Add pressure gauges before the first stage and after the last stage. This differential is your maintenance indicator.

- If adding UV, install after filtration with proper flow control and a normally closed solenoid if the unit faults (per manufacturer guidance).

4) Seal and Pressure Test

- Wrap male threads with Teflon tape (PTFE), tighten to spec without over-torquing plastic.

- Grease O-rings lightly and seat evenly; hand-tighten sumps, then a snug turn with the wrench.

- Close bypass, open inlet slowly, then open outlet. Check all joints. If sweating copper, pressure test after cool-down.

5) Flush and Commission

- Flush carbon cartridges until water runs clear and odor fades—often 5–10 minutes per stage.

- Record static and dynamic pressure, baseline differential (e.g., 2 psi). Note install date on each housing with a marker.

- If UV is installed, disinfect the plumbing loop per manufacturer instructions and verify lamp status.

Maintenance and Monitoring

Change sediment filters when pressure drop doubles from baseline or when visibly loaded; for many homes that’s 3–6 months. Carbon cartridges are capacity-based—track gallons or rely on time (6–12 months) backed by taste/odor return. UV lamps typically require annual replacement; sleeves need periodic cleaning. The pressure gauges pay for themselves by preventing premature changes and catching clogged stages early.

Safety, Materials, and Sustainability

- Use potable-water-rated materials and lead-free valves to comply with current plumbing codes.

- Keep cartridges out of direct sunlight; carbon can become a microbial bed if left stagnant—consistent usage and timely changes are key.

- Consider a scale-control approach over traditional salt softening if sodium discharge is a concern; if you softenen, regenerate efficiently and check local discharge guidelines.

- Recycle polypropylene cartridges where facilities exist; some municipalities accept them with plastics after rinsing and drying.

Troubleshooting the Common Issues

- Low pressure at fixtures: check sediment preload and carbon micron rating, confirm valves fully open, verify housing orientation and flow direction.

- Air hammer or noise: add water hammer arrestors near quick-close valves (dishwasher, laundry).

- Leaks at housings: re-seat O-rings, ensure no double-gasketing, avoid overtightening.

- Chlorine taste returning quickly: undersized carbon or chloramine on municipal water—move to catalytic carbon or larger capacity.

Planning the Mechanical Wall Layout

For tight utility rooms, I mock up the assembly so filters stagger and clear each other during service. Keep the UV ballast high and dry, leave straight runs for flow meters or future add-ons, and make sure the bypass is intuitive for guests or sitters. If you’re pre-planning pipe runs or a utility corner refresh, a quick pass through a room layout tool can help simulate clearances, working reach, and maintenance swing space before you drill a single hole.

room layout tool

When to Call a Pro

If your test shows bacteria, high iron with staining, or rotten-egg odor, the solution often involves oxidation, contact tanks, backwashing media, and UV—those systems require more plumbing skill and controls. Gas water heaters near the work zone, complicated manifolds, or code-specific backflow requirements are also good reasons to bring in a licensed plumber.

FAQ

1) How do I calculate peak flow for sizing?

Add typical fixture flows for simultaneous use: e.g., two showers at 2.0–2.5 gpm each, dishwasher 1.5–2.0 gpm, and a faucet at 1.0–1.5 gpm. Size your filter bank so pressure drop stays acceptable at that total (often 8–12 gpm in small homes).

2) What micron rating should my sediment filter be?

Start coarse, then refine. A 20–10 µm first stage protects a 5 µm second stage when water is dirty. If water is generally clear, a single 5–10 µm pleated filter keeps pressure loss moderate.

3) Is carbon block or granular carbon better?

Carbon block offers tighter filtration and longer contact time but higher pressure drop. Granular activated carbon (GAC) flows easier but can channel if not well-designed. For chloramine, catalytic carbon is the safer bet.

4) Do I need UV if I’m on city water?

Typically no, if residual disinfectant is present and your plumbing is in good condition. If you have frequent boil advisories, immunocompromised residents, or a remote property with storage tanks, UV adds a margin of safety.

5) How do I know when to change filters?

Use the pressure gauges: when the differential doubles from your initial reading, the sediment stage is loaded. For carbon, track taste/odor and the manufacturer’s gallon rating; set a 6–12 month reminder.

6) Will a whole-house filter remove hardness scale?

Standard cartridges won’t. For hardness, use a softener (ion exchange) or a scale-control system (TAC) that crystallizes minerals to reduce adhesion. Choose based on water test, maintenance tolerance, and local discharge rules.

7) Can I filter only hot or only cold water?

Whole-house systems treat cold water before it feeds the water heater, covering both hot and cold lines. Never run hot water through standard filter housings—they’re not rated for high temperatures.

8) How do I protect outdoor irrigation capacity?

Plumb outdoor hose bibs upstream of the filter bank. This preserves carbon capacity and keeps your irrigation flow unrestricted.

9) What about pressure regulators and expansion tanks?

If city pressure exceeds 80 psi, add or adjust a pressure reducing valve (PRV). Closed systems with a PRV should include a thermal expansion tank on the water heater to prevent relief valve discharge.

10) Are stainless steel housings worth it?

They’re durable and temperature-tolerant but cost more. For most homes, quality HDPE/PP sumps with metal heads are sufficient if properly mounted and maintained.

11) How do I size UV correctly?

Match the UV unit’s rated flow to your peak demand and ensure prefiltration to reduce turbidity. Sleeves must be clean; lamps replaced annually for consistent dose.

12) Can I install the system on PEX?

Yes. Use support brackets, bend supports, and brass or polymer fittings rated for potable water. Keep radius bends gentle to avoid kinks near housings.