Questions to Ask a Filtration Supplier

Choosing a water filtration system is not like buying a kettle. Get it wrong and you end up with expensive equipment that doesn’t address your actual water quality, or a supplier who disappears the moment the invoice is paid. The questions below are designed to expose the difference between a supplier who understands your water and one who simply sells pre-configured packages.

Why the first question is always about testing

Every suburb in Johannesburg can have meaningfully different water. Borehole water in Kyalami has a different mineral profile to borehole water in Randburg, and municipal supply quality varies by zone and by season. A supplier who recommends a system before testing your water is working from assumptions, not data.

Ask directly: Do you conduct a water test before recommending a system, or do you work from a standard package?

A credible supplier will either test on-site with a basic field kit or send a sample to a laboratory before specifying anything. If they say testing isn’t necessary, that’s a significant warning sign. The relevant benchmark for drinking water in South Africa is SANS 241 (2024 edition), and the only way to know whether your water meets or deviates from it is to measure.

For a broader look at what filtration options exist and how they fit together, the water filtration guide on this site walks through the main system types without the sales pitch.

Questions about their technical qualifications

Filtration suppliers range from specialist water engineers to generalist plumbers who have added filters to their service list. Neither is automatically bad, but you need to understand what you’re dealing with.

Ask:

• Are you registered with a relevant trade body or do your installers hold plumbing certifications?
• Who specifies the system design — an in-house technician or the manufacturer’s rep?
• Have you worked with Johannesburg Water’s supply conditions specifically, including the region’s elevated non-revenue water losses and the variability that comes with a system running close to its 27-hour storage buffer?

That last question is worth raising because water quality in Johannesburg can fluctuate — pressure changes and supply interruptions affect sediment load and can stress poorly chosen filter housings.

Questions about the system they’re proposing

Once a supplier has done their homework and is recommending a specific solution, push them on the details:

What contaminants does this system actually remove? Get a list. Vague claims about “purifying” or “improving” water aren’t useful. You want to know which parameters — sediment, chlorine, chloramines, nitrates, hardness, microbial load — the system addresses and to what reduction level.

What does it not remove? Every filter type has limitations. Reverse osmosis removes a wide range of dissolved solids but wastes water in the process and strips out beneficial minerals. Carbon filters handle chlorine and organics but won’t touch dissolved heavy metals. A supplier who can’t tell you the gaps is overselling.

What are the ongoing costs? Filter media and membranes need replacing. Ask for a realistic annual running cost estimate, including consumables and a service call. This is where pre-packaged deals often look cheap upfront and expensive over five years.

Question to ask	What a good answer looks like
Do you test water before specifying?	Yes — field test or lab sample before any recommendation
Which SANS 241 parameters does this address?	Specific list, not a general claim
What does the system not remove?	Honest acknowledgement of filter-type limitations
What are annual running costs?	Itemised estimate including consumables and service
What’s your post-installation support process?	Named process, not a vague promise

Questions about installation and compliance

A filtration system that’s plumbed in incorrectly can contaminate rather than clean. Ask:

• Will the installation comply with local bylaws and SANS standards?
• Who signs off on the work, and will I receive documentation?
• If the system connects to my municipal supply, how do you handle the backflow prevention requirements?

For more on evaluating the people doing the physical work, the guide on how to choose a water filtration installer covers the installer-selection side of this decision in more detail.

If you want to put these questions to real suppliers without doing the legwork yourself, you can compare 3 free quotes from vetted installers — no obligation.

Questions about after-sales support

This is where many suppliers fall short. Water quality changes over time — especially in Johannesburg, where municipal supply can vary by season and borehole levels fluctuate with rainfall. A system specced for your water today may need adjustment in two years.

Ask:

• Do you offer periodic water re-testing as part of a maintenance agreement?
• If my water quality changes significantly, will you respecify the system or just replace consumables?
• How do I reach you if there’s a fault — is there a direct technical contact or a call centre?

A supplier confident in their product will welcome these questions. One who becomes vague or defensive when you ask them is telling you something important.

Red flags to watch for

A few patterns consistently indicate a supplier more focused on closing a sale than solving your problem:

• Recommending a system at the first meeting, before any water data
• Quoting only one option with no explanation of alternatives considered
• Being unable to name the SANS standard their system is designed around
• Pressure tactics around limited-time pricing or installation slots
• No written maintenance or support terms

Pricing varies considerably depending on what your water actually needs. As a rough guide, backup tank-and-pump systems typically run R20,000–R40,000, while more comprehensive whole-house treatment setups can be higher — but the right starting point is always your water test results, not a brochure.

Before you commit to any supplier, it's worth seeing how their proposal compares. Get 3 quotes from installers who test first — vetted, no pressure.

What a good supplier conversation actually looks like

A supplier worth hiring will ask you questions too — about your water source (municipal, borehole, or both), how many people are in the household, whether you’ve had any taste or odour complaints, and whether you’ve seen any plumbing discolouration. They’ll want to see a recent municipal water quality report if you’re on the grid, and they’ll schedule a water test before putting anything in writing.

If the conversation goes that way, you’re dealing with someone who is trying to match a solution to a real problem. If it goes straight to a product demonstration and a quote, keep looking.