Low Loss Header Installation Loughton
- 2 days ago
- 5 min read
Fixing an 18-Radiator Worcester Regular System That Wouldn't Heat the Back of the House
If radiators at the far end of a large property aren't heating up while the boiler runs constantly on full pump speed, the cause is often a flow rate problem rather than a faulty boiler. On a recent job in Loughton, we resolved exactly this by fitting a custom-made low loss header and an additional circulator pump to a Worcester Bosch Greenstar CDi Classic Regular boiler serving 18 radiators and a hot water cylinder.
This is a common issue on larger homes in IG10 and the surrounding Loughton, Buckhurst Hill and Woodford Green area, where older heating systems were designed for far fewer radiators than they're now being asked to run.
The Problem
The homeowner called us out with a familiar complaint: the radiators at the back of the house simply weren't getting warm, no matter how long the heating was left running. On inspection, we found a system under serious strain
The boiler's pump was running flat out on maximum speed permanently, with no let-up
The boiler was short cycling — firing up, hitting temperature limit, switching off, then firing again moments later — rather than modulating down and running steadily
There was no proper condensing action taking place, which meant the boiler was operating well below its rated efficiency and likely costing far more to run than it should
Several components on the system were leaking
The existing setup — a Grundfos pump, Drayton 2-port zone valves, and a standard expansion vessel — was being asked to push flow around 18 radiators plus a hot water cylinder, all from a single circuit
In short, the single pump and primary circuit simply couldn't deliver enough flow to reach every radiator in the property. The nearest radiators were getting more than their share of hot water, while the ones furthest from the boiler — typically at the back of the house — were starved of flow and staying cold.
Why This Happens on Larger Heating Systems
A standard Regular boiler is designed and rated to push water around a primary circuit at a set flow rate. That works well on a modest system with a handful of radiators. Once you're into double digits — and especially once you reach 18 radiators plus a cylinder — the pipework resistance across the whole system can exceed what a single circulator and the boiler's own pump can realistically overcome.
When that happens, the boiler's pump has to work harder just to keep any water moving, which is exactly why we found it running on maximum speed continuously. The boiler itself was also struggling to modulate properly — instead of throttling down its gas valve as the system approached temperature, it was cycling on and off, which is both inefficient and puts unnecessary wear on the components.
The Fix: Custom Low Loss Header and Additional Circulator
Rather than replace the boiler — which wasn't the actual fault — we addressed the root cause: flow.
We designed and fabricated a custom low loss header specifically sized for this system. A low loss header hydraulically separates the boiler's primary circuit from the wider distribution side of the system. This means the boiler always sees the steady flow rate it needs to run efficiently and modulate correctly, regardless of how many zones or radiators are calling for heat on the building side.
Alongside the header, we fitted an additional circulator pump dedicated to the secondary (distribution) side of the system. This took the load of pushing water to all 18 radiators and the cylinder off the boiler's own pump entirely, splitting the job into two manageable circuits:
Primary circuit: boiler to low loss header, maintaining the flow rate the boiler is designed for
Secondary circuit: low loss header out to the radiators, zone valves and cylinder, driven by the new dedicated circulator.
We also resolved the leaking components found during the survey and reviewed the existing Drayton 2-port valve arrangement and expansion vessel sizing as part of the same visit, to make sure the rest of the system was fit to support the new header design.
The Result
With the low loss header and second circulator in place:
The previously cold radiators at the back of the house began heating properly
The boiler's own pump no longer needed to run at maximum speed permanently
The boiler was able to modulate down and run continuously at a lower, steadier output instead of short cycling
Proper condensing action was restored, improving running efficiency
This is a common pattern we see across larger homes in Loughton and the wider IG10 area - long extensions, loft conversions, or simply older properties with more radiators added over the years than the original system was ever designed to support.
How Do You Know If You Need a Low Loss Header?
A low loss header isn't always the answer, but it's worth investigating if you're seeing:
Radiators at one end of the property consistently colder than the rest
The boiler pump running constantly on full speed
Frequent boiler cycling rather than steady running
A boiler that never seems to properly condense or reach its rated efficiency
A larger heating system (typically 12+ radiators plus a cylinder) on a single circulator
If any of this sounds familiar, the issue is very likely hydraulic rather than a fault with the boiler itself — and it's worth a proper flow assessment before any parts get replaced unnecessarily.
Why Choose LHS Plumbing for Low Loss Header Installations in Loughton
Our engineers are Gas Safe registered and manufacturer-approved installers for Viessmann and Vaillant, as well as fully experienced across Worcester Bosch systems. We hold G3 qualification for unvented hot water cylinders, and we design every low loss header and secondary pumping arrangement around the actual flow demands of your property — not a one-size-fits-all part off the shelf.
We cover Loughton, Buckhurst Hill, Woodford Green, Chingford, Wanstead, Chigwell and Epping.
Call 020 8111 1230 to book a flow and heat loss assessment for your property.
Frequently Asked Questions
What is a low loss header and what does it do?
A low loss header is a hydraulic separation device fitted into a heating system. It separates the boiler's primary circuit from the rest of the building's pipework, so the boiler always has the flow rate it needs to run efficiently, regardless of how many radiators or zones are operating on the distribution side.
Why wasn't my boiler heating all the radiators in my house?
This is most often a flow rate problem rather than a boiler fault. On larger systems, a single pump can struggle to push enough hot water all the way to radiators furthest from the boiler, leaving them consistently cold while nearer radiators heat normally.
Do I need a low loss header if I have a lot of radiators?
Not always, but it becomes more likely the larger the system. As a guide, systems with around 12 or more radiators plus a hot water cylinder running from a single circulator are the ones most likely to benefit from hydraulic separation.
Will a low loss header work with my existing Worcester, Vaillant or Viessmann boiler?
Yes. A low loss header is fitted into the pipework rather than the boiler itself, so it can be retrofitted to most existing Regular, System or combi boiler installations, including Worcester Bosch Greenstar Regular models.
Why was my boiler cycling on and off instead of running steadily?
Boiler cycling typically happens when the boiler reaches its set temperature too quickly and shuts off, rather than modulating its output down and running continuously. Restricted or excessive flow caused by an undersized circuit, as found on this job, is a common cause.
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