Bathroom Plumbing

ComGas carries out the plumbing, heating and electrical work behind bathroom, en-suite and cloakroom projects across Farnham, Guildford and the surrounding area — first and second fix pipework, moved soil and waste, and shower pressure sorted properly. We're the plumbing contractor on the job, not a bathroom design or fitting service.

Discuss Your Bathroom Plumbing Call 01252 214120

The plumbing behind the finish

We handle the pipework and connections — not the tiling or the bathroom suite itself.

A bathroom project has two distinct halves: the plumbing, heating and electrical work that goes on behind and beneath the finished surfaces, and the tiling, waterproofing and fitting that create the finished room. We do the first — first and second fix pipework, waste routing, shower and cylinder considerations — and coordinate closely with whoever does the second.

That boundary matters because it decides who to call for what, and it means our advice on layout, pipe runs and waste positions is genuinely about what's plumbable, not about what looks good in a brochure. Where a layout the homeowner or designer wants isn't straightforward to achieve, we'll say so before work starts rather than after the tiling is up.

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How we approach bathroom plumbing

Pipework, waste and pressure worked out before the finishing trades start.

Every bathroom job is planned around first and second fix sequencing, waste routing and the existing hot water system, coordinated with the wider building or renovation work.

First and Second Fix Bathroom Plumbing

Bathroom plumbing happens in two stages, and getting the sequencing right avoids opening up finished walls or floors later to fix something that should have been caught earlier.

First fix covers pipework, soil stack and waste routing before walls and floors are closed up
Second fix covers connecting and commissioning taps, showers, basins and WCs once the room is decorated and tiled
We carry out the plumbing and heating first and second fix; tiling, fitting the bathroom suite and waterproofing are carried out by others and coordinated around our work
Correct sequencing avoids reopening finished surfaces to correct a plumbing issue that should have been resolved at first fix

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Moving Soil and Waste Pipework

Repositioning a WC or shower affects fall, venting and pipe diameter, and whether it's straightforward depends entirely on the existing soil and waste routing.

Moving a WC or shower any real distance from the existing soil stack affects fall, venting and pipe diameter, and needs proper assessment rather than assumption
A macerator unit allows a WC to be sited where a conventional gravity soil connection isn't practical, at the cost of some noise and an added point of maintenance
Waste pipe falls and venting need to meet Building Regulations Part H, particularly on longer runs
Loft or second-floor bathroom additions often depend entirely on whether the waste routing down through the house is genuinely achievable

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Shower Pressure, Pumps and Wet Rooms

Shower performance is governed by the hot water system behind it far more than by the shower valve chosen, and a wet room's plumbing needs deciding before the waterproofing goes in.

Shower pressure and flow depend on whether the system is combi, gravity-fed or unvented — not primarily on the shower valve itself
A pump can boost pressure and flow to a gravity-fed system, but pump selection and siting need to suit the cylinder and pipework rather than being added as an afterthought
Wet rooms need drainage falls and pump or gravity waste designed at first fix, before the waterproofing and floor build-up are installed
Combi boilers can struggle to maintain strong pressure to more than one outlet running at once, which matters when planning a second bathroom

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Co-ordinating Plumbing with Bathroom Renovation Work

We're the plumbing, heating and electrical contractor on a bathroom project, not a design or fitting service, so we plan our work to fit around the wider trades rather than in isolation.

We're not a bathroom design or fitting service — tiling, bathroom furniture and waterproofing are scoped and delivered by others
First fix is planned and sequenced with the builder or fitter so pipework, waste and electrics are in place before finishing trades start
Where an existing bathroom's plumbing constrains the design — pipe runs, waste falls, cylinder capacity — we flag it before work starts rather than after tiling is done
Layout changes agreed once tiling begins are far more disruptive, so we work from a fixed, agreed layout wherever possible

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It starts with the hot water system

The shower you can fit depends on the hot water system already in the house.

A shower valve on its own can't overcome a weak hot water supply. On a combi boiler, pressure at the shower is broadly the mains pressure, shared with anything else drawing water at the same time — good in principle, but it can dip noticeably if someone runs a tap elsewhere. On a gravity-fed system, pressure depends on the height of the cold water tank above the shower, and is often too low for a satisfying shower without a pump.

An unvented cylinder gives strong, even, mains-pressure-equivalent flow to every outlet in the house without a tank or pump — which is one reason it's often specified where multiple bathrooms need to run well at the same time. We check which of these systems is already in place, and what a proposed new bathroom would need from it, before recommending a shower or a pump. Cylinder types and sizing are covered in more detail on our hot water cylinders page.

Combi boiler: mains-equivalent pressure, shared with any other outlet in use at the same time
Gravity-fed system: low pressure unless boosted with a correctly sized pump
Unvented cylinder: strong, even pressure delivered to every outlet independently
Pump and system choice checked against the existing setup before any shower is specified

Discuss Your Bathroom Plumbing

Genuine feedback

What homeowners say about ComGas.

Reviews from real ComGas customers, shown as submitted through Google.

Bathroom plumbing questions

Frequently asked questions.

If you're planning a new bathroom, en-suite or wet room, get in touch and we'll confirm what the existing plumbing and hot water system can support.

Call 01252 214120

Do you design and fit bathrooms?

No — we carry out the plumbing, heating and electrical work behind a bathroom project. Design, tiling, fitting the bathroom suite and waterproofing are carried out by others, and we coordinate our first and second fix around that work.

Can a WC or shower be moved to a different part of the bathroom?

Often, yes, but it depends on the existing soil stack position, achievable falls and venting for the new location. We assess the specific layout before confirming what's practical.

Why is my shower pressure poor even though the pipe looks fine?

It's usually the hot water system behind the shower, not the pipework to it — a gravity-fed system without a pump, or a combi boiler under demand from another outlet, are the most common causes. We check the system type before recommending a fix.

What is a wet room and does the plumbing need to be different?

A wet room has a level, waterproofed floor with the whole room designed to drain to a single point rather than a shower tray. The drainage fall and any pump needed for the waste have to be designed into the floor build-up at first fix, before waterproofing goes down.

Can I fit a second bathroom on a combi boiler system?

Often yes, but simultaneous use of two showers or a bath and a shower together may reduce pressure and flow at both. We assess the boiler's output and the mains supply before confirming whether a second bathroom will perform well on the existing system.

What is a macerator and when is one needed?

A macerator is a small pump-and-grinder unit that allows a WC to be plumbed into a waste pipe where a conventional gravity connection to the soil stack isn't practical, such as a basement conversion. It adds some noise and an extra serviceable component compared with a standard connection.

How do you coordinate plumbing work with the builder or tiler?

We agree a sequence with the builder or fitter so first fix pipework, waste and electrics are complete and tested before decorating and tiling begin, and second fix connections happen once the room is finished. Timing is confirmed before work starts, not worked out as we go.

Do you carry out waterproofing or tanking for wet rooms?

No — waterproofing and tanking are carried out by the tiler or building contractor as part of the finishing work. We design and install the drainage and pipework it needs to work around, and coordinate timing with whoever carries out the waterproofing.

Start a conversation

Planning a new bathroom, en-suite or wet room?

Tell us about the layout you have in mind and the existing hot water system, and we'll confirm what's plumbable before work starts.

Call our team01252 214120 Email enquiriesinfo@comgas.uk

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Bathroom Plumbing

We handle the pipework and connections — not the tiling or the bathroom suite itself.

Pipework, waste and pressure worked out before the finishing trades start.

First and Second Fix Bathroom Plumbing

Moving Soil and Waste Pipework

Shower Pressure, Pumps and Wet Rooms

Co-ordinating Plumbing with Bathroom Renovation Work

The shower you can fit depends on the hot water system already in the house.

What homeowners say about ComGas.

Frequently asked questions.

Planning a new bathroom, en-suite or wet room?

Discuss Your Bathroom Plumbing

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