A new boiler on a dirty system.
The line on the quote nobody looks for

If you are having a new boiler installed, there is one thing on the quote that many people never look for, and I would say it matters more than the price. That is whether the system is being cleaned for your new boiler or not.

A brand new boiler installed on a dirty old system is a boiler running on borrowed time, and when you eventually call the manufacturer out for a warranty visit, you may well find that the visit is not covered at all.

Why it gets
left off a quote

I want to be fair about this, because it is not always somebody cutting corners. Cleaning out a heating system takes time, and time is the most expensive part of any boiler installation quote. So when somebody is working to undercut another installer, this is one of the first things to come out of the price, and it is easily missed by the person reading the quote.

It is also invisible at the time. The boiler goes on the wall and it works, and it works for a good while, until it does not. The trouble arrives later. It could be weeks, it could be months, it could be a couple of years. And because it arrived so much later, and because everything was fine at the start, most people never connect it back to the day the boiler went in.

What is actually happening
inside the system

Over the years sludge builds up in a heating system, in the radiators, in the pipework and in the old boiler too.

Modern boilers are built to run more efficiently. They have more sensors and they are more sensitive, and to get that efficiency they have finer waterways inside them than the older ones did. Those wider passages are gone. So when water carrying debris passes through a modern heat exchanger, it can cause blockages.

Put a brand new boiler with all of that on a dirty system, and you are effectively pumping all that dirt into your new boiler. It is not the boiler's fault, because the manufacturers tell us it is designed to run on a clean system, so it is our job as installers to make sure the system is clean and ready before that boiler goes anywhere near the wall.

The warranty part

This is the part that catches people out, because manufacturers insist the system is clean and most of them insist their own magnetic filter is fitted with the boiler, which is why a filter is a requirement on most installations. Many of them will not honour the warranty if they find the system is dirty and there is no filter fitted. They have refused to carry out warranty work in the past until a system has been cleaned.

So you may have paid for a long warranty on your boiler. On a dirty system with no filter, it may be worth very little. And you will not find that out on the day it is installed. You find out weeks, months, or a couple of years later, at the point you need it.

We have had instances where clients have contacted us to powerflush their radiators and heating system because the manufacturer refused to repair the boiler as it was installed on a dirty system. Some manufacturers can be very strict about this even if the fault you are having is nothing to do with a dirty system because in their eyes the installer has not adhered to their rules.

Three things to ask,
and none of them are technical

Get it in writing that the system will be flushed. Ask what chemicals are going to be used, and ask whether a good quality inhibitor is going into the system afterwards.

Ask whether a filter is being fitted. Then ask where it is going, what quality it is and which brand.

Check the paperwork at the end. When the install is finished you get the documentation for the boiler and for the installation. Make sure the benchmark is filled in, and that the cleaning section is completed properly, so it is written down what chemicals were used to flush your system and what inhibitor went in.

Anyone doing the work properly will be happy to answer all three, because they are describing work they were going to do anyway.

Not every system needs a
power flush

One thing I will say is that not every system needs a power flush. It depends on the system, and some will need a power flush where others only need a chemical flush. What is true of every one of them is that it needs to be cleaned, and it is the installer's job to work out which is right and to make sure it is done properly.

So speak to whoever is quoting and ask them plainly whether a flush is being done and what kind of flush it will be. The quote that does not mention cleaning at all is the one to look out for.

The short version

The line on a boiler quote that matters most is the one about cleaning the system, and it is the line most people never look for. Cleaning takes time, time is the expensive part of an installation, so it is the first thing cut when a quote is being undercut. Modern boilers have finer waterways and more sensors, so old sludge causes blockages in them. Manufacturers insist on a clean system and usually on their magnetic filter being fitted, and many will not honour the warranty if they find the system dirty with no filter. Before you sign, get the flush in writing along with the chemicals and the inhibitor, ask about the filter, and check the benchmark and the cleaning section are filled in at the end.

Quick answers