Unleash Sparkling Clarity: The UK Guide to Choosing Pool & Spa Filters

Why the Right Pool Filter Matters

Think of a pool filter like the heart of your swimming setup: it keeps water moving cleanly and keeps the whole system healthy. A struggling filter means cloudy water, algae parties, and chemistry chaos. Pick the wrong type or size and you’ll fight the water every weekend. Pick the right one and your pool will be clear as a bell, your chemicals will behave, and maintenance becomes a breeze.

Types of Pool Filters Explained

There are three main filter types you’ll see at B&Q, Screwfix, Wickes, and specialist retailers like Poolbits and Hayward UK: sand, cartridge, and diatomaceous earth (DE). Each works differently, so let’s break them down into plain English.

Sand Filters: Simple and Robust

Sand filters use a bed of special sand to trap debris. They’re reliable, low-maintenance, and perfect for larger pools up to 20,000 gallons or more. Backwash every few weeks and you’re good. Expect water clarity down to about 20–30 microns, which is fine for family pools and outdoor setups. Sand filters are often the budget-friendly option available at stores like Wickes and Screwfix.

Cartridge Filters: Cleaner Without Backwashing

Cartridge filters trap particles on a replaceable paper or synthetic element. They can capture finer debris than sand—typically down to 10–15 microns—and don’t require backwashing, which saves water. You’ll clean cartridges every 1–3 months and replace them every 1–3 years depending on usage. Cartridge filters are a popular choice for pools around 10,000–15,000 gallons and are widely stocked by B&Q, Poolstyle, and online sellers such as Amazon UK and eBay.

DE Filters: The Gold Standard for Clarity

Diatomaceous earth filters offer the finest filtration, capturing particles down to 2–5 microns. That means sparkling water that looks like glass. They’re commonly used in commercial or high-end residential pools and for spas that demand ultra-clear water. DE systems require periodic backwashing and recharging with DE powder; you’ll find DE units and supplies at specialist outlets and manufacturers such as Hayward UK and Zodiac.

How to Size a Filter for Your Pool

Sizing matters more than brand glitz. An undersized filter works overtime and shortens equipment life; oversized equipment wastes money. The key is turnover rate—the time it takes to filter all the pool water. Aim for a turnover of 8–10 hours for most pools and 4–6 hours for busy public or commercial pools.

Quick Sizing Example Using Imperial Units

Let’s say you have a 12 ft by 24 ft rectangular pool, 4 ft average depth. That’s about 12 x 24 x 4 = 1,152 cubic ft. Multiply by 7.48 gallons per cubic ft ≈ 8,614 gallons. For an 8-hour turnover, required flow = 8,614 gallons ÷ (8 hours × 60 minutes) ≈ 18 gpm (gallons per minute). Choose a filter and pump that handle at least 18 gpm, plus a safety margin. Retailers like Screwfix and B&Q list pumps with gpm specs so you can match them accurately.

Top UK Retailers to Buy Pool Filters

Where you buy affects price, warranty, and support. Here are reputable UK places to shop, each with strengths.

B&Q

B&Q offers a solid mix of cartridge and sand filters, plus accessories. Good for DIY homeowners who want a local option and a clear returns process. You’ll find entry-level systems that suit pools up to around 15,000 gallons.

Screwfix

Screwfix is a go-to for robust, trade-grade kit. They stock pumps and sand filters often used by pool pros. If you’re installing a pump and filter yourself, Screwfix has practical accessories like union fittings and pressure gauges.

Wickes

Wickes caters to those who prefer home-improvement convenience with garden and pool ranges. Their selection suits above-ground and small in-ground pools and is convenient for fitting into a wider garden project.

Pool Specialists (Poolbits, Poolstyle, The Pool Shop)

Specialist retailers focus on pool-grade cartridge, DE, and sand filters plus genuine replacement parts from Hayward, Zodiac, and other big names. If you want brand-matched parts or advice on matching your filter to an existing pump, these are excellent places to shop.

Online Marketplaces (Amazon UK, eBay)

Online marketplaces give huge choice and competitive pricing. Watch out for genuine sellers and product specs—especially when matching micron ratings and flow rates. Amazon UK often stocks branded filters and kits with quick delivery; eBay can be good for hard-to-find replacement elements.

Choosing Between Installed Systems and DIY Kits

Are you replacing a filter on an established pool or starting from scratch? For new installs, you’ll need to match pump capacity, pipe diameter, and filter type. For replacements, measure your current system and bring specs when shopping. DIY kits at B&Q and Screwfix make installations straightforward, while specialist stores can supply tailored systems if your pool has unusual needs.

Matching Pipework and Unions

Pipes in home pools are often 1½ in. or 2 in. diameter. Make sure the filter and pump unions match your plumbing, or plan to buy adaptors. Mismatched pipe sizes reduce flow efficiency and can cause cavitation or poor filtration.

Maintenance: Keep Your Filter Running Smoothly

Maintenance is where many pools win or lose. A bit of routine care keeps filters effective and extends life. Let’s go through simple, practical steps.

Sand Filter Care

Backwash a sand filter when the pressure gauge rises about 6–8 psi above clean baseline. You’ll backwash until water runs clear—typically about 2–5 minutes—and then rinse for 30–60 seconds. Replace sand every 5–7 years or when it becomes rounded and ineffective.

Cartridge Filter Care

Cartridge filters need cleaning every 1–3 months depending on use. Remove the cartridge and hose it down; for deep cleaning, soak in a cartridge cleaner overnight. Replace cartridges when the pleats show damage or flow never recovers after cleaning—usually every 1–3 years.

DE Filter Care

Backwash DE filters when pressure climbs 8–10 psi over baseline, then recharge with fresh DE powder following the manufacturer’s dosage. DE grids last several years with proper handling, though eventual replacement is inevitable if cloth becomes damaged.

Signs It’s Time to Replace Your Filter

How do you know a filter is tired? Cloudy water after shocking, constant high pressure, or a pump struggling are red flags. If you clean cartridges and flow doesn’t improve, or if sand has hardened into channels, it’s time to upgrade. Replacing a filter before it fails prevents bigger headaches like pump burnout or expensive algae eradication.

Filters for Spas and Hot Tubs

Spas and hot tubs have their own filtration needs. They typically require compact cartridge filters sized for smaller water volumes—often under 500 gallons. Because water is heated, biological load is higher, so filter cleaning is more frequent—every 2–4 weeks for regular use. Brands like Hozelock and Hayward make spa-specific cartridges available through retailers and specialist suppliers.

Cost Considerations and Budgeting

How much will a filter cost? Expect entry-level cartridge filters under £100, mid-range sand systems from £150–£400, and commercial-grade DE or high-capacity sand systems costing £500 or more. Don’t forget recurring costs like replacement cartridges, DE powder, and occasional sand replacement. Shop deals at B&Q or Screwfix for seasonal discounts, and compare specialist quotes for installation if you’re not DIYing.

Eco-Friendly Choices and Water Savings

Water conservation is a growing concern—especially if you operate a pool during dry spells. Cartridge filters save water because they don’t require backwashing, while modern sand filters with lower backwash frequency help too. Consider pairing a low-water-loss cartridge or sand system with a pool cover to cut evaporation and chemical use. Retailers increasingly stock eco-friendly options and guidelines to reduce water use.

Tips for Buying: Get the Right Warranty and Parts Availability

A good warranty and easy access to spare parts are worth paying for. Hayward and Zodiac parts are widely available from specialist suppliers, giving peace of mind. Check that replacement cartridges, O-rings, and pressure gauges are sold separately and aren’t proprietary-only items that become hard to source in a few years.

DIY Installation vs Hiring a Pro

If you’re comfortable with basic plumbing—measuring flow rates, matching unions, and sealing threads—you can install many consumer-grade filters yourself. If your system includes gas heaters, complex pipework, or large pumps, hire a qualified technician. A botched install can cause leaks, poor flow, or damage to your pump—expensive mistakes that are worth avoiding.

Making the Right Choice: A Simple Checklist

Here’s a quick mental checklist to pick the right filter: pool volume in gallons, desired turnover hours, pump flow in gpm, pipe diameter, maintenance willingness, and budget. Start with volume and turnover, choose the filter type that fits your cleanliness needs, then match flow and pipe size. That approach removes guesswork and narrows your options to what retailers like B&Q, Poolstyle, or Poolbits actually stock.

Real-World Example: Upgrading a 10,000-Gallon Pool

Imagine a 10,000-gallon backyard pool used by a family of four. For an 8-hour turnover you need around 21 gpm. A mid-range cartridge filter paired with a pump rated for 25–30 gpm gives margin and avoids constant strain. Buy a cartridge with 10–15 micron rating, and plan to clean every 4–6 weeks during heavy use. You’ll find suitable kits at Screwfix, Poolbits, or through online marketplaces.

Summary of Where to Shop and Why

For general DIY and affordability, visit B&Q or Wickes. For trade-grade hardware and pumps, check Screwfix. For specialist parts, brand matches, and expert advice, go to Poolbits, Poolstyle, or The Pool Shop. For choice and convenience, online marketplaces like Amazon UK offer fast options. Compare prices and read product specs closely—especially micron ratings and gpm limits—before you buy.

Conclusion

Picking the right pool or spa filter in the UK comes down to clarity, sizing, maintenance appetite, and budget. Sand, cartridge, and DE filters each have strengths, and shops from B&Q to specialist retailers provide options to fit nearly any pool. Use turnover calculations in gallons and gpm to match pump and filter, keep up with routine maintenance, and don’t hesitate to lean on specialist stores for brand-specific parts. With the right setup, you’ll spend less time skimming and more time enjoying crystal-clear water.