Industry Guides· 3 min read· By The SpideyChat Team

Unvented Cylinder and Hot Water Enquiries

A household running out of hot water needs a system decision, not a quote. A decision guide on what actually suits a property.


A family of five run out of hot water every morning. They have been told they need a new boiler, they have been told they need a cylinder, and they have been told the problem is the shower.

All three might be right. Nobody has measured anything.

Start with demand, not with product

How many people, how many bathrooms, whether showers run simultaneously, whether there is a bath and what the morning routine actually looks like. This determines the answer more than anything else.

Measure the incoming supply

Flow rate and pressure at the property. An unvented cylinder needs an adequate supply and installing one on a poor mains produces a system that disappoints in a different way.

Explain the options honestly

A combination boiler, a vented cylinder with a tank, an unvented cylinder, or a heat source with a cylinder. Each suits a different household and none is universally better.

Explain the space requirement

Cylinders need somewhere to live, with access for servicing and the associated equipment. Customers removing a tank to gain a loft are sometimes surprised by what replaces it.

Explain the annual servicing requirement

Unvented systems require periodic checks by a suitably qualified person, and customers should know this before choosing. Publishing it is honest and creates a maintenance relationship.

Explain the safety components

Expansion, pressure relief and discharge arrangements exist for reasons and must be installed correctly by someone qualified to do it. Saying so plainly distinguishes a proper installer.

Ask about the existing system

Age, type, where things are and what has changed recently. A system that worked for years and stopped has a different cause to one that never coped.

Explain what a conversion involves

Pipework, the discharge route, electrical work, making good and how long the household is without hot water. Customers budget for a cylinder and not for the work around it.

Be honest about the cheaper fix

Sometimes a shower, a pump or a valve solves the problem for a fraction of the cost. Saying so loses a large job and earns a customer who will call you for everything else.

Publish indicative ranges

By system type, with what drives the price. Customers need to know whether they are in the right conversation before booking a survey.

Capture what makes a recommendation possible

Property type, bathrooms, occupants, current system, where things are, what the problem is and whether anything changed, which is the qualification in receptionist screening questions.

Explain the recovery time

Customers judge a system on whether there is hot water when the second person wants a shower, and that is about how quickly a cylinder reheats rather than how big it is. Explaining recovery rates, and what determines them, is what stops somebody buying the largest cylinder that fits and still running out on a Monday morning.

Pressure complaints arrive the same way

They are covered in water pressure complaints and what plumbers ask, and ongoing servicing is covered in boiler service and annual check questions.

Getting started

Publish the options, indicative ranges and what you need to know, then capture demand and system details at any hour and pass jobs into your systems through integrations. SpideyChat for plumbers answers from your published pages, much as remote working households are served in desk and office enquiries from remote workers. Try SpideyChat on your own site, or read about capture on the features page.

Frequently asked questions

What is an unvented cylinder?
A pressurised hot water cylinder fed directly from the mains, which requires suitable incoming supply and specific installation requirements.
Is a combination boiler better than a cylinder?
It depends on the household, since combination boilers suit lower simultaneous demand and cylinders suit higher.
What determines which hot water system suits a property?
The number of bathrooms, simultaneous demand, incoming mains flow and pressure, available space and the existing system.

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