10" Double Big Blue Whole House Water Filter System – 5 Micron Sediment & Tannin Reduction Cartridge

A two-stage Big Blue whole house filtration system pairing a 5-micron sediment pre-filter with a tannin-selective reduction cartridge. Designed for properties on private water supplies – boreholes, springs and wells – where naturally occurring tannins from peat, decaying vegetation and leaf litter give water a yellow or tea-coloured tint and an earthy taste.

Both cartridges are supplied with the system and use the universal 10" x 4.5" ("Big Blue") format, so future replacements stay simple.

What tannins are – and why a standard filter won't shift them

Tannins are large organic molecules that leach into water from peat, leaves and decaying roots. They're not harmful to drink, but they leave their mark in three ways:

• Discolouration – water comes out the tap with a yellow, amber or "weak tea" tint.
• Staining – fixtures, sinks, laundry and toilet bowls pick up brown marks over time.
• Taste and odour – an earthy, musty or astringent character that sediment and carbon cartridges don't fully remove.

Standard sediment and carbon filters can't capture tannins because the molecules are too small for mechanical filtration and bind too loosely to activated carbon. They need a dedicated anion-exchange media designed specifically for this job.

How the two stages work

• Stage 1 – 5 Micron Sediment: captures rust, sand, silt and pipe scale that would otherwise stain fixtures, block aerators and shorten the life of appliances. Just as importantly, it protects the tannin cartridge in Stage 2 – sediment fouling shortens the life of any ion-exchange resin, so a clean pre-filter directly protects your investment in the tannin media.
• Stage 2 – Tannin Reduction Cartridge: packed with a tannin-selective anion-exchange resin. The resin attracts the negatively charged tannin molecules and exchanges them for chloride ions, leaving water visibly clearer and free of the earthy taste tannins cause.

Important – will this work on your supply?

Tannin cartridges work brilliantly when matched to the right water, but they're more sensitive to feed water conditions than sediment or carbon filters. Before ordering, please consider:

• Hard water: calcium and magnesium foul tannin resin and shorten its working life dramatically. If your supply is hard, we'd recommend installing a water softener upstream of this system.
• Iron and manganese: high levels of either will also coat and disable the resin. These are best dealt with by a dedicated iron filter ahead of the tannin stage.
• Chlorine: tannin resins handle low to moderate chlorine, but heavily chlorinated supplies should be carbon-filtered first.
• Tannin level: cartridge life depends entirely on how much tannin is in your water. Lightly tea-tinged water will give you many months between changes; heavily stained water may need replacement every few weeks.

If you're not sure whether tannin is the right answer for your discolouration, we're always happy to talk it through – contact us with a sample or a description of what you're seeing and we'll point you in the right direction.

Compatibility

• Standard 1" female BSP inlet and outlet ports – a straight fit on UK whole-house plumbing.
• Accepts any standard 10" x 4.5" ("Big Blue") cartridge, so the housing can be repurposed for sediment, carbon or specialist filtration if your needs change.
• Suitable for cold mains feeds in domestic and light commercial settings.

Technical specifications

If your incoming mains pressure exceeds 6 bar (≈88 psi), fit a pressure regulator upstream. UK mains pressure is typically well within range, but it's worth checking before installation.

Installation notes

The system is designed for wall mounting at the point of entry, downstream of your stopcock. We'd recommend installing isolation valves on the inlet and outlet so cartridge changes are quick and tidy.

Replacement intervals depend entirely on local water quality. As a guide: sediment every 6 months; the tannin cartridge anywhere from 1 to 12 months based on the tannin load in your supply. Many customers find it useful to keep a spare tannin cartridge on hand once they've established a baseline.

What's included

• 10" Double Big Blue twin filter housing with mounting bracket
• 5 Micron Sediment cartridge (Stage 1)
• Tannin reduction cartridge (Stage 2)
• Filter bowl wrench
• Wall mounting screws
• Spare housing O-rings
• PTFE (Teflon) tape
• Instruction guidance

Follow the manufacturer’s installation guidance, confirm all connections are secure and flush the product as instructed before regular use.

Order before our dispatch cut-off — 3pm Monday to Friday, or 12pm on Saturday — and your order is sent the same day; anything after that follows the next working day. We don’t dispatch on Sundays, and you’ll get a tracking link by email as soon as your order is on its way.

Choose your UK delivery option at checkout:

• Free Express Delivery — free on orders over £60 (2–3 working days).
• Standard Delivery — £3.99 (2–3 working days).
• Next Day Delivery — £6.99, arriving the next working day when you order before the cut-off.

We also ship internationally, with rates calculated at checkout.

Returns & refunds

Changed your mind? You have 30 days to return any unused filter in its original sealed packaging for a refund, or 90 days for exchanges. Start at our returns portal and either generate a prepaid Royal Mail label (£3.49, deducted from your refund) or use your own courier — exchanges are always free to return. We approve refunds within 24 hours of your return reaching us; your bank may then take 3–5 working days to show the funds.