PHAM NEWS | JULY/AUGUST 2026 30 Pipes, Fittings & Valves


The high cost of substitution


A leaking joint can turn a minor product failure into a major liability claim. As substitutions and mixed- manufacturer systems become more common, installers need to understand where warranty protection ends and where costly risk begins – so says Arne Glass from Brymec.


Put them together and you have interfaces nobody has tested, with a warranty trail that quietly unravels.


Warranty caveats Manufacturer warranties aren’t the safety net most installers assume. They are commercial documents with strict conditions, and those conditions exist so that claims can be challenged. Take press-fit. To honour the


Arne Glass Specification manager, Brymec


P


icture the scene: 12 months after handover, water is finding its way through a ceiling that


should never have leaked. By the time the failure has been traced back to the joint that gave up, somebody is being asked to write a very large cheque. The question is whether that somebody is you. According to the Association of


British Insurers, escape of water claims cost UK construction roughly £2.5 million every day. More often than the trade likes to admit, it is the installer left carrying the loss, not because the work was poor, but because the liability was built into the job by procurement decisions made long before anyone reached site.


Risk horizon The ‘equal or approved’ clause has quietly become the biggest single source of compatibility risk on UK projects. The vast majority of technical submissions still involve late swaps, and most are driven by price rather than performance. On a spreadsheet they look sensible. On site, the trouble starts when those components are asked to work together as a system. The result is too often a


mixed-manufacture, sometimes mixed-material installation that nobody really owns. A fitting from one brand sits next to a valve from another, joined to tube from a third. Each component may be compliant in isolation.


warranty of up to 30 years on Brymec’s Stainless Steel Press-fit System, we require the installer to hold a current certificate of training issued by us, to use approved press tools maintained to the manufacturer’s requirements, to install on Brymec 316L stainless steel tube and to retain all commissioning paperwork. Other manufacturers run comparable terms. Now picture the substitution.


The specified system is swapped for a cheaper alternative. The installer trained on system A is asked to press system B with a tool that may or may not meet the replacement manufacturer’s approved list. A year on, a joint starts dripping above a server room. The replacement brand reviews the paperwork, sees no training certificate for their system, and the claim is denied. Here’s the part the trade rarely


talks about openly. Even when a warranty does pay, it pays on the product. Manufacturer terms typically exclude indirect or consequential loss. A £10 valve fails and the £50,000 of damage to the flat below lands with someone else. That someone is usually the installer, the main contractor or their insurer.


Mix of materials The mixed-material issue runs deeper still. Plastic-to-metal connections are the classic example. Plastics expand significantly more than metals under temperature change, and that differential movement stresses joints, loosens seals and gradually works the connection apart. The failure rarely comes from one bad component. It comes from joins where thermal movement was never calculated across three different manufacturers’ kit. It also


p When every component is designed to work together, installers are less exposed to the risks of substitution and mixed- manufacturer systems


comes from the gaps where one supplier’s responsibility ends and the next has not started. None of this shows up at commissioning. It surfaces two winters later, when the cost of access and remediation has multiplied. M&E consultants are feeling


the same pressure. They are being asked to demonstrate genuine design assurance, not generic clauses. But by the time the job reaches the installer, the original specification has often been rewritten through a chain of substitutions that nobody properly documented.


Single source There’s a more straightforward way to de-risk this. It starts with whole-system thinking at specification stage and a closer eye at submission. Ask which party owns the interface between fitting and tube, or between different materials, such as cast iron connecting to HDPE drainage. That connection can be compliant when it stays within one manufacturer’s range and uses the correct interface components. The moment


and commissioning paperwork lines up with what the manufacturer expects to see.


it crosses manufacturers, ownership becomes a live question. Single-source supply removes


the ambiguity. Our hybrid model means we own the journey from factory to site with in-house logistics and stand behind the end-to-end system, not just a single component. One point of contact, one technical team, one coordinated warranty position. That model also protects the installer’s training and tooling investment. Certificates stay valid against the system they were issued for, approved tools match the fittings on the van,


Three habits You don’t need a law degree to push back on any of this. Three checks at submission stage will catch most of the trouble before it lands. One, actually read the warranty terms, not just how many years it runs for. Two, every ‘equal or approved’ substitute that crosses a system boundary requires a written compatibility question and a documented answer. Three, specify a consistent manufacturer whose components carry tested, compatible interface details. That is what qualifies the


installation for a coordinated system warranty, rather than a patchwork of individual product cover. If a single-source supply isn’t available, pinpoint exactly where the terms stop and confirm in writing who owns the risk. Leaks aren’t going away. But


the installers who treat warranty conditions as part of the job, rather than something to skim past at submission, are the ones least likely to be explaining themselves to an insurer twelve months on. ◼ phamnews.co.uk/726/66


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