A whole house reverse osmosis system filters all water entering your home at a single point - before it reaches any faucet, shower, toilet, or appliance. Unlike an under-sink unit, it treats the whole supply. Up to 99% of dissolved solids, metals, and chemicals removed: lead, fluoride, arsenic, chlorine, nitrates, PFAS.

Quick summary

• Whole house RO treats every tap in the house, not just the kitchen
• Installed at the point of entry (POE) - water is treated before it goes anywhere
• Flow rates run 300 GPD to 3,000+ GPD; match to household size
• Most installations need a storage tank and a repressurization pump
• NSF/ANSI 58 certification is the benchmark to look for - don't skip it

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How does a whole house reverse osmosis system work?

Water comes in and hits several pre-filter stages first - usually a sediment cartridge and a carbon block. The carbon matters: chlorine destroys RO membranes fast, so it has to go before the membrane sees the water.

Then the RO membrane does the actual work. Semi-permeable, roughly 98% rejection rate on a decent thin-film composite (TFC) membrane. Purified water goes to a pressurized storage tank; concentrate goes to drain.

From the tank, a booster pump moves water through the house at normal pressure. A post-carbon filter polishes things at the end. That's the full loop.

Typical stages:

1. Sediment pre-filter (5-20 micron) - particles, rust, sand
2. Carbon pre-filter - chlorine and chloramines
3. RO membrane (TFC, 98% rejection rate)
4. Storage tank (40-200 gallon depending on household)
5. Repressurization pump
6. Post-carbon polish filter
7. UV sterilization (optional but worth it for well water)

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What does whole house reverse osmosis actually remove?

Contaminant	Removal rate
Lead	95-99%
Fluoride	90-96%
Arsenic	92-98%
Nitrates	85-95%
PFAS (forever chemicals)	90-95%
Chlorine	95-99%
Chloramines	85-95%
TDS (total dissolved solids)	92-99%
Bacteria	99%+
Heavy metals (chromium, cadmium)	95-99%

These numbers come from NSF/ANSI 58 testing protocols. Your actual results depend on feed water TDS, temperature, and how recently the membrane was replaced. A well-maintained membrane at 2 years old performs differently than one at 5 years.

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What does a whole house RO system cost?

Equipment runs $1,500-$8,000 depending on capacity.

• 300-500 GPD (1-2 people, city water): $1,500-$2,500
• 1,000-2,000 GPD (3-4 bedroom home): $2,500-$4,500
• 3,000+ GPD (large home or well water with high TDS): $4,500-$8,000+

Installation adds $300-$1,000. Annual filter replacements and membrane checks run $150-$400. A good system lasts 10-15 years.

The cost-per-gallon math usually lands below $0.01 - cheaper than buying water by the case, and you're getting it from every tap.

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How to choose the right system

Test your water first. Seriously. Municipal water and well water are not the same problem, and a system sized for city water at 200 ppm TDS won't handle a well at 800 ppm. A certified lab test costs $50-$150 and tells you exactly what you're dealing with.

Match GPD to household size:

• 1-2 people: 300-500 GPD
• 3-4 people: 750-1,500 GPD
• 5+ people or heavy use: 2,000+ GPD

TDS above 500 ppm means you probably need a larger membrane or a two-pass setup. Brackish or salt water is a different category - that requires a specialized SWRO system.

NSF/ANSI 58 certification is not optional. It's independent testing that confirms the system actually reduces contaminants to the levels claimed. If a vendor can't point to it, walk.

Plan for the tank. Every whole house RO system needs a storage buffer. Gravity-fed setups lose pressure at the tap. Size the tank to your daily demand and pair it with a properly rated pump.

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Whole house RO vs under-sink RO

	Whole house RO	Under-sink RO
Treatment point	Point of entry	Point of use
What it covers	Every tap, shower, appliance	Kitchen faucet
Flow rate	300-3,000+ GPD	50-100 GPD
Installation	Professional plumber	Usually DIY
Equipment cost	$1,500-$8,000+	$200-$600
Best fit	Well water, high TDS, appliance protection	Drinking and cooking water only

If you only care about drinking and cooking, the under-sink is the economical call. But if your water has known contamination - lead in old pipes, arsenic from groundwater, PFAS from a nearby industrial site - or if you want to protect your water heater and appliances from scale and chemicals, the whole house system is the right call.

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Whole house RO vs water softener

A softener removes calcium and magnesium through ion exchange. That's it. It won't touch lead, arsenic, nitrates, or PFAS. A whole house RO removes hardness minerals and the rest.

Use a softener alone if hardness is your only issue. Use RO if you have chemical contamination, high TDS, or well water with unknowns. In very hard water areas, some customers run a softener before the RO system - the softener handles the hardness, which extends membrane life considerably.

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Our whole house RO systems

Ampac Water Systems builds residential and commercial RO systems in the US. NSF/ANSI 58 certified membranes, factory technical support, and field experience across residential, municipal, and industrial applications.

Residential options:

• Under-sink RO (50-200 GPD) for point-of-use
• Whole house RO (300-3,000 GPD)
• Water softeners and conditioners
• UV sterilization systems
• Alkaline and remineralization filters

Browse residential systems | Request a quote | Call (909) 548-4900

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Updated May 2026 | Ampac Water Systems | Ships nationwide | Made in the USA