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Expansion Vessel
Pre-charge checked and set in line with the manufacturer's instructions for your cylinder — not left at the factory precharge. This is the single most common thing I find set wrong.
water_heaterG3 Qualified
G3 Unvented Hot Water Cylinder Servicing & Repair
Annual servicing, fault repair and pre-purchase inspections on unvented cylinders across Orpington, Bromley, Petts Wood and Chislehurst. £140 with no VAT, and you get a written inspection record every time.
verified_userG3 Qualified
descriptionWritten Record Issued
money_offNo Call-Out Fee
paymentsFixed Price Servicing
- check_circle£140 — full G3 annual service, no VAT
- check_circle£270 — cylinder + heat pump serviced together
- descriptionWritten inspection record every visit
- personYou deal with me, Gary — not a call centre
- near_meLocal to Orpington & Bromley
Smith EcoFlow carries out G3 qualified unvented hot water cylinder servicing, repair and pre-purchase inspection across Orpington, Bromley, Chislehurst, Sidcup and Sevenoaks. A full annual service is £140 with no VAT and includes expansion vessel pre-charge, temperature and pressure relief valve testing, expansion relief valve testing, thermal cut-out testing, discharge pipework checked against Approved Document G3, inlet control group and strainer, and a written inspection record. Combined with a heat pump service in the same visit it is £270. Brands include Megaflo, Gledhill, Telford, Joule, RM Cylinders Stelflow, Vaillant and Heatrae Sadia. Book on 07717 846247.
Real Work
A real job: pre-purchase inspection, Tower Road, Orpington
A buyer wanted the hot water system checked before completing. The survey had barely looked at it. I found an undersized discharge manifold that did not comply with Approved Document G3, an expansion vessel still at its 2020 factory pre-charge, and low boiler primary pressure. The buyer went in with a costed list of remedial work rather than a surprise six months later.
Read the full case study →checklistWhat's Included
What a Proper G3 Service Covers
An unvented cylinder is a pressurised vessel. Its safety devices are what stand between normal operation and a genuinely dangerous failure — so they get tested properly, every one of them.
thermostat
Safety Valves Tested
Temperature and pressure relief valve tested, expansion relief valve tested, and the thermal cut-out checked. All three are tested, not just looked at.
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Tundish & Discharge Pipework
Checked against Approved Document G3 — pipe sizing, routing, termination and the visible air break. Undersized discharge manifolds are a common non-compliance.
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Inlet Control Group
Pressure reducing valve, check valve and strainer checked and cleaned. A blocked strainer is a frequent cause of poor hot water pressure.
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Immersion & Thermostat
Immersion heater and thermostat checked, and stored water temperature verified — hot enough to be safe from bacteria, not so hot it scalds.
description
Written Record
Benchmark logbook completed and a Domestic Unvented Hot Water Storage Vessel Inspection Record issued — the paperwork your warranty and your buyer's solicitor will want.
buildCommon Faults
Problems I See Most Often
Written from actual jobs, not a manufacturer's brochure.
Water discharging from the tundish
The most common call I get. It means a safety valve is passing, and the usual culprit is the expansion vessel — either it has lost its charge, or it was set to the wrong pressure at commissioning. I once found a vessel charged 0.5 bar above what the incoming mains could deliver, which left it unable to absorb expansion properly. Never ignore a discharging tundish.
Expansion vessel losing charge or set wrong
Vessels lose air over time, and a great many are never commissioned to suit the property in the first place — they are left at the factory precharge from the year they were made. The pre-charge should be set in line with the manufacturer's instructions for your cylinder, using properly taken pressure readings. Checking and resetting it is part of every service I do.
Failed temperature and pressure relief valve
These can weep, stick, or fail to reseat after operating. A weeping T&P valve wastes water and signals a fault upstream. Replacement is straightforward and I carry the common sizes.
Blocked strainer and low hot water pressure
If your hot water pressure has dropped off but the cold is fine, the strainer in the inlet control group is a likely cause. It fills with debris from the mains and is easy to clean once you know where to look.
Non-compliant discharge pipework
I regularly find two 15mm relief valve discharges combined into a single 15mm manifold — which does not comply with Approved Document G3. It matters, because in a genuine over-pressure event the pipework has to be able to carry the discharge safely away.
verifiedBrands
Cylinders I Work On
All major unvented cylinder manufacturers, whoever installed them.
MegafloGledhillTelford
JouleRM Cylinders StelflowVaillant
Heatrae Sadia
gavelWhy G3 Matters
Not Just Anyone Can Work On These
Work on an unvented hot water cylinder over 15 litres requires the G3 qualification under Building Regulations. That is not red tape for its own sake — a badly maintained pressurised cylinder is genuinely dangerous, which is why the law restricts who is allowed to touch one. Always ask to see a G3 certificate. I am happy to show you mine.
Buying or selling a house?
I carry out pre-purchase cylinder inspections for buyers and vendors, and issue a written report with photographs — covering the condition of the cylinder, whether the safety devices function, whether the discharge pipework complies with Approved Document G3, and anything that needs putting right. It is a small cost against the price of a house, and it is producing a steady stream of enquiries because most surveys do not look at the cylinder in any detail.
starReal Reviews
What Cylinder Customers Say
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"Gary repaired my hot water cylinder for me. My cylinder stopped working so I telephoned Gary. I explained I was elderly and he turned up in 45 minutes. He repaired/charged the expansion vessel and all is working perfectly again. I definitely recommend Gary."
Peter GilbertOrpington · Cylinder Repair
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"Gary came out and sorted our unvented cylinder, replacing the PRV. Professional, tidy and explained everything clearly. Would use again."
Jennifer LakeUnvented Cylinder · PRV Replacement
helpFAQ
Unvented Cylinder Questions
Once a year. It is a pressurised vessel, and annual testing of the safety devices — the temperature and pressure relief valve, the expansion relief valve and the thermal cut-out — is the accepted standard. Most manufacturer warranties also require documented annual servicing.
It means a safety valve is passing. Most often the expansion vessel has lost its charge or was set to the wrong pressure, but it can also be a failed temperature and pressure relief valve or expansion relief valve. Do not ignore it — it means the system has nowhere safe to expand.
Building Regulations require anyone working on an unvented hot water cylinder over 15 litres to be competent to do so, and the G3 qualification is the recognised route to demonstrating that competence. A pressurised cylinder that is not properly maintained is genuinely dangerous, so the law restricts who can work on one. Always ask to see the certificate.
Yes — for buyers and vendors. You get a written report with photographs covering the cylinder condition, the safety devices, the discharge pipework and G3 compliance, plus anything that needs putting right.
£140 with no VAT for a full G3 annual service including the written inspection record. If you also have an air source heat pump, both serviced in one visit is £270. Repairs are quoted separately at a fixed price agreed before I start.
All the major brands — Megaflo, Gledhill, Telford, Joule, RM Cylinders Stelflow, Vaillant and Heatrae Sadia — regardless of who installed them.
See real cylinder jobs
Read a pre-purchase inspection that found an undersized discharge manifold, and a repair where the fault turned out to be a commissioning error rather than a broken part.
Read the Case StudiesplaceAreas
Cylinders — Areas, Brands & Faults
Dedicated pages for the areas, brands and faults I deal with most.
OrpingtonBR5, BR6, Petts Wood, Chelsfield, Crofton
BromleyBR1–BR4, Beckenham, Bickley, Hayes
ChislehurstBR7, Petts Wood, Bickley
SidcupDA14, DA15, Blackfen, Bexley
SevenoaksTN13–TN15, Riverhead, Otford
Megaflo Servicing & RepairEco, Eco Plus & SystemReady faults
Tundish Dripping?What it means and what it costs
Losing Pressure?Hot down, cold fine — the usual causes
photo_cameraOur Work
What Gets Tested on Every Visit
Every safety device tested, not just looked at.
Book Your Cylinder Service
£140 with no VAT, a written inspection record every time, across Orpington, Bromley, Petts Wood and Chislehurst.
call07717 846247