Whole House Filtration Installation

Purpose

A point-of-entry filter is a deliberate restriction in front of every fixture in the building, sized by two numbers the box does not lead with: the flow at which the media still works, and the pressure the house can afford to lose. Get either wrong and the customer gets a shower that fades when the laundry starts, and is right to blame the plumber. A carbon unit also strips the disinfectant residual from every foot of pipe downstream, which the customer should decide knowingly rather than discover.

Scope

Covers selecting, placing and installing a point-of-entry sediment or carbon filter, cartridge or backwashing, on the cold main of a house, duplex, small retail unit, small restaurant or office.

Does not cover drinking water devices at a single tap, owned by the point of use filter selection and installation SOP, nor water softening, nor the diagnosis that decides whether treatment is the right answer, owned by the water quality complaint visit SOP. Does not cover expansion control sizing, owned by the expansion tank verification SOP, which this procedure hands off to.

Roles and responsibilities

Procedure

1. Measure the water before you select anything. Acceptance: static pressure at a hose bib with nothing running, pressure again at a stated flow with a known fixture open, service size and material, and the treatment target from a laboratory result. What wrong looks like: a unit picked on service size alone, which says nothing about what the house has to spend on pressure. Stop rule: static above the range the adopted plumbing code allows means a pressure reducing valve conversation first, under its own SOP. Hazard: a gauge can be driven off a pressurized bib, so close the bib, fit it hand tight plus a quarter turn, then open slowly standing to the side of the outlet.
2. Size to the unit's rated service flow, never to its maximum flow. Service flow is the flow at which the media still has contact time to do the job it is certified for; maximum flow says only what the housing will pass. Acceptance: design flow computed by the adopted plumbing code's method in the edition your jurisdiction enforces, and rated service flow at or above it. What wrong looks like: a maximum flow on the carton read as capacity, on a unit whose service flow is half that. Stop rule: a rated service flow below the design flow is not installed; go up a size or run two in parallel. Hazard: none here, arithmetic at the tailgate, and the step that prevents the callback.
3. Set the pressure-drop budget from the pressure the house actually has, and install a gauge each side. Acceptance: static pressure, minus the clean-cartridge drop read from the manufacturer's curve at design flow, minus elevation at 0.433 psi per foot up to the highest fixture, minus piping loss at design flow, leaving a stated margin above that fixture's flowing minimum from its own manufacturer - computed at the clean drop and again at the change-out drop. The change-out trigger is twice the clean drop at the same flow, or the labeled interval, whichever comes first. What wrong looks like: a change-out schedule with no gauges behind it, a guess wearing a date. Stop rule: a budget that misses the highest fixture's minimum at the change-out drop means the unit is too small for this house. Hazard: none here, but the arithmetic gets written down, because whoever answers the low-pressure call in two years is not the one doing it now.
4. Place it where the plumbing wants it and where the next cartridge change is possible. Acceptance: on the cold main after the meter and any backflow preventer, downstream of the pressure reducing valve where one exists so the housing sees regulated pressure, upstream of the heater, with a full bypass, unions and a shutoff each side, and clearance below the sump to swing down. What wrong looks like: a unit hung on the pipe itself, carrying a flooded housing's weight on a soldered joint. Stop rule: no sump clearance and the unit is relocated, not fitted tight; a filter that cannot be serviced is not serviced. Hazard: a large housing is heavy at chest height, so bracket it into structure and use two people rather than holding it while threads start.
5. Decide the residual question out loud, and record the customer's answer. A carbon unit at the point of entry removes the disinfectant residual from every foot of pipe downstream, which is the point on taste and a real trade-off everywhere else, and it matters most with long unused branches, low occupancy or a heater stored low. Acceptance: the trade-off stated in writing, the decision recorded, and the mitigations named where they accept it - keeping storage temperature up with fixture-side tempering under its own SOP, using the seldom-used branches, or leaving one tap unfiltered. What wrong looks like: a carbon unit sold on chlorine taste with nothing said. Stop rule: a building with a known stagnation problem does not get the unit until the mitigation is agreed. Hazard: none here, a conversation, and the one that makes the install defensible.
6. On a backwashing unit, treat the drain as indirect waste and put the electrical work where it belongs. Acceptance: the drain discharged through an air gap into a receptor sized for the backwash flow rather than the service flow, per the adopted plumbing code's indirect waste provisions in the edition your jurisdiction enforces, and a receptacle within reach of the control valve's cord with ground fault protection where the code requires it. What wrong looks like: a backwash line pushed into a standpipe with no air gap, a direct connection to drainage. Stop rule: no air gap, no commissioning, and no extension cord as the supply. Hazard: water beside an energized control, so receptacle work goes to an electrician where nobody on site is qualified under 29 CFR 1910.332, with work practices at 29 CFR 1910.333(b)(2).
7. Cut in and support the unit, with a control named for each thing you are about to release. Acceptance: the main isolated and drained before cutting, the unit hung independently of the piping, unions square so the housing is not pulled, and every joint made per the material's instruction. What wrong looks like: a housing pulled into alignment by tightening unions, which cracks months later. Stop rule: piping that will not meet the unit without strain gets a repositioned bracket, not a pulled joint. Hazard: each act releases something different - solvent cement gives off vapor, so ventilate and follow the safety data sheet rather than working in a closed closet; soldering or brazing produces flux fume and an ignition source, so ventilate, keep a fire watch and clear combustibles behind the joint; drilling masonry for anchors releases respirable crystalline silica, needing water or vacuum dust control under 29 CFR 1926.1153 on construction work, with 1910.1053 as the general-industry counterpart.
8. Repressurize, purge, hold, then prove every protective function you may have disturbed. Acceptance: the main reopened slowly with a fixture open to bleed air; the unit purged for the manufacturer's stated volume until clear of fines; a hold at full line pressure for a stated period with every joint dry to a paper towel; the bypass operated and proved to actually bypass; the reducing valve still holding its setting; the heater's relief discharge dry with its piping intact; expansion control present and connected, handed to the expansion tank SOP where a check has made this a closed system; and both gauges read at design flow as the clean baseline. What wrong looks like: a system left pressurized with the bypass never tested, found on the first cartridge change when the house cannot be isolated. Stop rule: a weeping joint is remade and the hold restarts; a relief valve discharging after the install stops the job and goes to the expansion control SOP. Hazard: this puts full pressure back with the customer nearby, so open the main slowly, keep faces out of line with the housing seam, and stand clear of the relief discharge outlet, which delivers water hot enough to scald if it lifts.

The record this produces

One install record: static pressure and pressure at a stated flow; the computed design flow and the method used; the unit model with both its rated service flow and its maximum flow; the pressure budget worked at the clean and the change-out drop, showing elevation and the highest fixture's flowing minimum; the clean differential baseline read at design flow; the placement relative to meter, reducing valve and heater; the residual decision and its mitigation; the hold result; and the bypass, reducing valve, expansion control and relief checks.

The clean differential baseline is what makes the change-out rule work. Without it, twice the clean drop is an unanswerable question and the shop falls back to a calendar, for a cartridge whose life depends entirely on this building's sediment.

One worked pass, including a failure

Two-storey house, 1990s, 3/4 in copper service, sediment and chlorine taste complaint, laboratory result showing nothing requiring a health claim. Step 1: static 68 psi at the laundry bib. Step 2: design flow computed for the fixture count comes to 9 gpm.

Step 2 fails. The unit first proposed carries a 15 gpm maximum flow on the carton and a rated service flow of 7 gpm, below the 9 gpm design flow. Stop rule taken: it is not installed, and the replacement is rated 12 gpm service flow.

Step 3, with the replacement: the manufacturer's curve read at 9 gpm gives a clean drop of 4 psi, so the change-out trigger is twice that, 8 psi at the same flow. The highest fixture is a second-floor shower 12 ft above the gauge, costing 12 times 0.433, that is 5.2 psi, and piping loss at 9 gpm is taken as 6 psi. Clean, the shower sees 68 minus 4 minus 5.2 minus 6, leaving 52.8 psi; at the change-out drop it sees 68 minus 8 minus 5.2 minus 6, leaving 48.8 psi. The shower valve's manufacturer states a 20 psi flowing minimum, so the budget clears at both ends and the unit is accepted.

Step 4: fitted on the cold main after the meter, downstream of the existing reducing valve, upstream of the heater, with bypass, unions, shutoffs and 5 in of swing clearance below the sump. Step 5: residual trade-off put in writing; the house is fully occupied with no long dead legs, the customer accepts, and the agreed mitigation is keeping storage temperature up with fixture-side tempering. Step 6: cartridge unit, no backwash drain or control valve. Step 7: main isolated and drained, unit bracketed into a stud, unions square, joints made per the material's instruction with the closet door open and a fire watch during soldering.

Step 8: main reopened slowly with a laundry tap open, purged until clear of fines, 30 minute hold at full line pressure with every joint dry, bypass operated and proved, reducing valve still holding its setting. The heater's relief valve then begins to weep, and the reducing valve is found to carry an integral check with no expansion tank. Stop rule taken: the job does not close; expansion control goes to the expansion tank verification SOP and is fitted before sign-off, after which the relief stays dry. Gauges read at design flow and the clean differential recorded as the baseline the change-out rule works from.

References

• The adopted plumbing code, in the edition your jurisdiction enforces, for the design flow method, the allowable system pressure range, and the indirect waste and air gap requirements for a backwash drain.
• Manufacturer literature for the unit's rated service flow, its maximum flow and its pressure drop curve; those are different numbers and both belong on the record, alongside the fixture manufacturer's flowing pressure minimum the sizing is defended against.
• 29 CFR 1926.1153 for respirable crystalline silica on construction work, with 29 CFR 1910.1053 as the general-industry counterpart, plus the safety data sheet for any solvent cement used.
• See related: the Plumbing point of use filter selection and installation SOP, the expansion tank verification on a closed system SOP, and the pressure reducing valve replacement SOP.