A $1,200 whole-home filter quote and a $2,800 quote for "the same thing" are almost never actually the same thing. The cheaper one might use a 10" housing where you need a 20", a carbon block rated only to NSF 42 where NSF 53 matters, no sediment pre-filter, and a 3-month cartridge life instead of 12. By the time you're buying cartridges every quarter and replacing the housing in two years, the cheaper quote cost more.
The problem isn't that suppliers are dishonest — it's that quotes are written to win the job, and without a standard set of questions, they will optimise for price rather than completeness. This guide gives you the tools to make three quotes genuinely comparable.
- →Get three written quotes. Phone quotes aren't comparable — written specs reveal what you're actually buying.
- ✗Don't compare on upfront price alone. A $1,200 system with $400/year proprietary cartridges costs more over 5 years than a $1,800 system with $120/year standard cartridges.
- ✓Every quote needs: filter stages + micron ratings, NSF certifications, cartridge model numbers and annual cost, warranty terms, bypass valve included.
- ✗Red flags: no written spec · "today only" pricing · vague "NSF certified" · proprietary cartridges · pressure to sign before getting other quotes.
- ✓Use the consultation checklist to run every supplier through the same 28 questions.
Before you request a quote
The quality of a quote is directly proportional to the quality of the brief you give. A supplier who receives "I want a water filter for my house" has every incentive to quote the lowest-cost system that technically qualifies. A supplier who receives a specific brief with your water data, your priorities and your property details has to respond in kind.
Gather the following before contacting anyone:
- Your water quality data. For Perth: use our suburb lookup tool and note your hardness, TDS, iron and pH. For other states: pull the relevant figures from your utility's annual report (our guide explains how). Suppliers who ask for this data before quoting are better than those who don't.
- Your mains entry size. Most residential properties have a 20mm (3/4") or 25mm (1") mains entry. Check the pipe where it enters your house or meter box. A system spec'd for 3/4" on a 1" mains entry will restrict your flow.
- Your household size and daily water use. Approximate litres per day, or just number of people and whether you have a garden. This affects filter sizing.
- What problem you're actually trying to solve. Scale? Chlorine taste? Iron staining? All three? Being specific prevents a supplier quoting an unnecessarily complex (or critically incomplete) system.
- Whether you own or rent. If renting, installation requires landlord consent and may need to be reversible.
What to ask each supplier
Send the same set of questions to every supplier you approach. This is the single most effective thing you can do — it turns an inherently unequal process into a structured comparison. Below is a template you can copy and send directly.
Hi, I'm looking for a whole-home water filtration system for my [X-bedroom home / X-person household] in [suburb]. My water data: hardness [X] mg/L, TDS [X] mg/L, iron [X] mg/L, pH [X]. My mains entry is [20mm / 25mm].
I'd like a written quote that specifies:
A supplier who responds to this with a full written answer has demonstrated they know their product and respect the process. A supplier who pushes back, gives vague answers, or says "just let us come and have a look" without providing specifications is giving you information about how they operate.
Getting a site visit before receiving a written specification is a sales technique, not a technical requirement. A supplier who refuses to specify what they're quoting until they're at your property is putting you in a position where you feel obligated once they've invested the time. It's completely reasonable to request written specs before agreeing to a site visit.
How to compare what you receive
Once you have quotes back, the comparison has several layers. Work through them in this order.
1. Is it actually addressing your water problem?
Before comparing prices, check that each quote actually contains the stages needed for your water. A quote for a chlorine-tasting town water supply should include a carbon block stage. A quote for a high-iron bore supply must include iron reduction media. If a quote doesn't address the specific parameters you provided, it's incomplete — ask why.
Use our water problem identifier if you're not sure what stages your water requires.
2. Are the filter housings appropriate for whole-home use?
10" × 2.5" housings are designed for under-sink point-of-use filtration. They restrict flow too much for whole-home applications — you will notice pressure drops throughout the house during peak use. Whole-home systems need 20" × 4.5" Big Blue housings (or equivalent flow-rated proprietary formats). If a quote for "whole-home filtration" uses 10" housings, ask the supplier to justify the sizing for your household flow demand.
3. What certifications does each stage carry?
This is where quotes diverge most significantly in real-world performance while appearing similar on paper. An NSF 42 carbon block and an NSF 53 carbon block look identical in a quote — "carbon block stage" — but one is tested for taste and odour only, while the other is tested for lead, cysts and VOC reduction. See our full certifications guide for what each standard covers.
4. What does the system actually cost per year to run?
The upfront installation price is the least important number in the total cost calculation. Work out the annual running cost for each quote:
- (Price per cartridge) ÷ (months it lasts) × 12
- Do this for each stage separately
- Ask if proprietary cartridges are only available through the supplier
- Check whether generic Big Blue replacements fit
- Is annual servicing required by warranty?
- What does a service call include and cost?
- Can you replace cartridges yourself, or must you use their technicians?
- Are cartridge replacements included in service visits?
- Installation price
- + (Annual cartridge cost × 5)
- + (Annual service cost × 5)
- = True 5-year cost
- Compare this number, not the upfront price
5. Is the installer licensed?
In all Australian states, connection to a mains water supply must be performed by a licensed plumber. This is not optional and is not waived for filter systems. Ask for the installer's plumbing licence number — legitimate operators will provide it without hesitation. An unlicensed installation creates warranty and insurance exposure if anything goes wrong with your plumbing.
WaterMark certification on the components is separate from the installer's licence. You need both. See the WaterMark section of our certifications guide for how to verify.
Red flags in quotes
| What it says in the quote | What to ask | Why it matters |
|---|---|---|
| "High-quality carbon block" | Which brand/model? NSF 42 or 53? What contaminants is it rated for? | NSF 42 = taste only. NSF 53 = health contaminants. These are very different products often described identically. |
| "5-stage system" | What is each stage, specifically? What does each one remove? | A second sediment stage and a redundant carbon stage both "count" as stages. Stage count is meaningless without specification. |
| "Certified system" | Certified to which standard? WaterMark, NSF 42, 53, 58? | WaterMark certifies plumbing hardware, not filtration performance. "Certified" without a standard number is often just WaterMark. |
| "Lifetime warranty" | What exactly does it cover? Is it transferable? What voids it? | Most "lifetime warranties" on filter housings cover manufacturing defects only and are voided by DIY cartridge changes or non-approved cartridges — which means you're locked into their service pricing. |
| No cartridge price listed | What is the cartridge replacement cost and interval? | A low upfront price sometimes reflects a business model based on proprietary, high-margin consumables. Know this before you commit. |
| "Removes 99.9% of contaminants" | Which contaminants? At what starting concentration? What test standard? | A 5-micron sediment filter removes 99.9% of particles above 5 microns. This claim tells you nothing about bacteria, chlorine, lead or anything else without specifics. |
| Quote sent within minutes of enquiry, no questions asked | Did they ask about your water quality data, mains size, or household use? | A legitimate system recommendation requires your water data. A quote produced without it is a generic template, not a tailored recommendation. |
After you've chosen a supplier
Before installation day, confirm in writing:
- The exact products being installed (brand, model number for each component)
- The installer's name and licence number
- That the installation will include a bypass valve and isolation valves on each housing
- What post-installation support looks like — who to call if there's a leak, how long before they can respond
On installation day, ask the installer to walk you through the shut-off procedure, where the bypass valve is, and how to remove the housing for a cartridge change. A supplier who installs a system and then makes it hard for you to maintain independently is not acting in your long-term interest.
Before making any calls, use our supplier comparison tool to check FO scores for the suppliers you're considering. The scores weight certifications, cartridge transparency, warranty terms and installation standards — all the things that are hardest to evaluate from a quote alone.