Planning a Bathroom Renovation? A Plumber's Guide to Getting It Right

A bathroom renovation is one of the most expensive home improvement projects you'll ever undertake. Done well, it adds genuine value and lasts decades. Done badly, you're back into the walls within five years fixing problems that should never have existed.

I do the plumbing side of bathroom renovations regularly across Orpington, Bromley, Sevenoaks and the wider Kent region — usually working alongside trusted local tilers, electricians and decorators. After 15+ years of bathroom work, here are the plumbing decisions that genuinely matter and the mistakes I see homeowners make again and again.

Plan the Plumbing Before You Plan the Look

This is the single biggest mistake — choosing your tiles and bathroom suite first, then trying to make the plumbing fit. The best bathrooms work the other way round.

Things to think about FIRST:

• Where is the soil pipe currently, and can it be moved? (Hint: usually yes, but it's expensive)
• What's your incoming water pressure? (Determines what shower system you can have)
• Is your hot water from a combi, system boiler with cylinder, or unvented cylinder? (Determines flow rates)
• What does the existing waste pipework look like? (Determines where the toilet, basin and bath/shower can go)
• Where do you want the radiator? (Towel rails are usually fine, full radiators need wall space)

Shower Systems: The Most Important Decision

The shower is what your customers (well, family) will judge the bathroom by. A weak shower with poor flow and unstable temperature ruins an otherwise perfect bathroom.

Mixer Showers

Take hot and cold supplies and blend them. Reliability and quality of flow depends entirely on water pressure and flow rates of your hot water system. Excellent with mains-pressure unvented systems.

Thermostatic Mixer Showers

Same as above but maintain temperature when other taps are used elsewhere. Essential for safety in family bathrooms — no scalding when someone flushes a toilet.

Electric Showers

Heat cold water on demand. Independent of your hot water system — useful for ensuites or where hot water demand is high. Generally lower flow rates than thermostatic showers fed by good hot water systems.

Digital Showers

Premium thermostatic showers with electronic controls. Excellent temperature stability and convenience features. Significantly more expensive but genuinely lovely.

Concealed vs Exposed Pipework

Concealed pipework (chased into walls) looks beautiful. But it's also a minefield if not done correctly:

• All joints must be done before tiling — no later access
• Pressure-test the system before walls go back up
• Use proper push-fit fittings rated for buried use, not just any pipe
• Mark the pipe routes for future reference
• Some areas (party walls, under load-bearing walls) restrict what can be chased

I always pressure-test the entire bathroom plumbing system at 1.5× working pressure before any tiling starts. If something's going to fail, I want it to fail before the tiler arrives.

Toilet Choice: Back-to-Wall vs Close-Coupled

Back-to-wall toilets with concealed cisterns look stunning. They also need:

• A proper frame with adjustable height
• Solid wall behind to mount it
• Service access via the flush plate (not a separate panel)
• Quality cistern brand — Geberit is the gold standard

Cheap back-to-wall systems are a false economy. The frame fails, the flush valve fails, and accessing the components is a nightmare. Spend properly here.

Basin Considerations

Three things people get wrong:

• Basin height — should be set to suit the tallest person who'll use it daily. 870mm is standard but I often install at 900–910mm.
• Tap height — make sure the tap clearance over the basin lets you wash your hands without splashing.
• Waste type — slotted vs unslotted matters. Slotted is needed for basins with overflows.

Heating: Towel Rail vs Radiator vs Underfloor

Many bathrooms now have heated floors. Done correctly, this is wonderful — warm tiles in the morning. Done badly, it's expensive to run and slow to warm up.

Decisions to make:

• Electric or wet underfloor? Wet costs more but runs cheaper.
• If keeping a towel rail, is it your only heat source? Most aren't powerful enough for the room — supplement with underfloor or a separate radiator.
• Smart thermostat? Highly recommend for energy management.

Waterproofing — The Most Important "Invisible" Job

Tanking (waterproofing) of wet areas is essential. Not all tilers do this properly. The tanking system should:

• Cover the entire shower enclosure floor and walls up to 2m high
• Cover the bath/shower area in similar fashion
• Use proper joint tape at all internal corners
• Be allowed to fully cure before tiling
• Be tested for water-tightness before tiling starts

Skimping on this is the most common reason for bathroom leaks 2–5 years after renovation. Insist on it being done properly.

Realistic Project Costs

For a typical full bathroom renovation in our area:

• Budget renovation: £4,000–£7,000 (basic suite, basic tiles, like-for-like layout)
• Mid-range: £7,000–£14,000 (quality suite, layout changes, decent tiles)
• High-end: £14,000–£30,000+ (premium fittings, complete redesign, luxury finishes)

Plumbing typically represents 20–30% of total cost. The other 70–80% is tiles, suite, electrical, decoration and labour for the other trades.

Working with the Right Trades

Smith EcoFlow handles the plumbing side. For the full bathroom, you'll need a tiler (specialist bathroom tilers are worth their weight in gold), a sparky for any electrical changes, and possibly a plasterer/decorator. We work alongside trusted local trades — happy to recommend people we know do good work.