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For a trade buyer, the practical upshot is that unvented spares are not interchangeable with vented ones. A pressure relief valve rated for an unvented system is a specific, tested part, not a generic valve that happens to fit the thread. The same goes for the expansion vessel, sized to the cylinder's stored volume, and the tundish and discharge pipework that safety fittings rely on to work as intended. Buying the wrong-rated part to save time on a job is a false economy at best.
Plumb2U carries the parts and spares for both instantaneous and storage electric water heaters, from elements and thermostats to the fittings that connect them into a system, at trade prices with next-day despatch across the UK. For merchants and installers working from a plumbers merchants account rather than a shop counter, that means the right spare is one order away, not a special one.
Learn more at plumbers merchants.
Plumb2U stocks both braided and rubber flexible hoses across the sizes and ratings trade buyers need, at trade prices with next-day despatch, so the choice comes down to the job, not what happens to be on the shelf.
Choosing between an electric shower and a mixer shower is not really a matter of preference; it comes down to what the property's existing hot water system can actually deliver, and the two options make very different demands on it.
More information is available at plumbers merchants.