What is the Boiler Replacement Process?

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It’s a heart-sinking moment when your boiler stops working. It feels as though everything is on hold; bathing, washing up, cleaning. So getting an engineer in quickly is a must. However, when you then receive the news that your boiler actually needs to be replaced, and can’t just be fixed, your heart can sink even further.

But we’d like to give you a little boost at this moment and reassure you that this doesn’t need to take as long as you think it will. When you choose a plumbing and heating company that deals with this stuff day in, day out, you can take heart that a new one will be up and running as soon as is possible.

What happens when you need to replace your boiler?

Well, your heating engineer will go through a few details with you first. For example, he/she will check how many bathrooms you have – or intend to have – and check your water pressure. They’ll also be keen to understand your usage levels and timings etc. as well. Once that’s established, you can then start your new boiler journey…

Homeowner Checking Boiler

Step-by-Step: The Boiler Replacement Process

Step 1 – Choose your new boiler. You’ll need knowledgeable advice to pick the right replacement, so we recommend you choose your adviser carefully. A qualified and experienced plumbing and heating engineer is your best bet.

Step 2 – The old boiler needs to be removed. Every job is different, but nothing can happen until that beast is out.

Step 3 – Your system then needs to be flushed and cleaned. It’s a requirement of British Standards, but the type of system you have will dictate what happens. You may just need a chemical flush, or you may need a power flush. And this is not a stage to miss, because a clean system will help to avoid damage to your new boiler in the future.

Step 4 – There may be upgrades to your pipework. Your installer may have recommended that your new boiler is sited in a different place, in which case you need adjustments made to your pipework. Plus, your new boiler may need adjustments and changes to be made to your pipework anyway. It’s likely boiler technology has improved significantly since your last boiler was installed.

Step 5 – Your boiler is fitted. This is when you start to feel real progress is being made.

New Boiler Replacement

Step 6 – Additional accessories are fitted. You may need a system filter, for example, to protect your boiler from any debris in your system. Plus you may need new controls. But all these things should have been agreed at the point of specification, so you shouldn’t be in for any surprises.

Step 7 – Testing. Once everything is installed, the engineer will commission the system by checking all aspects are working correctly. Combustion analysis is also undertaken to ensure the boiler is operating safely

Step 8 – Handover training. Once the engineer is happy the system is fine, he/she will take you through how the controls work, how to operate your new boiler, and any basic maintenance actions you should take.

Step 9 – Guarantee registration. One final step we recommend is that you then register your product with the manufacturer and ensure the guarantee is in place.

Step 10 – Enjoy your warm home with oodles of hot water!

To speak to someone about replacing your boiler, or to find out more about the boiler replacement process, please call us on 01908 034194.

Any questions?

If you are looking for a heating engineer within the Milton Keynes area for anything from boiler installations to fixing a tap, or would like some friendly advice please call Mitch directly today on 01908 034194

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Areas we cover

  • Aylesbury
  • Bedford
  • Leighton Buzzard
  • Northampton
  • Olney
  • Towcester
  • Woburn Sands
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What Our Customers Say

It’s not very often that you find a quality tradesperson who is reliable, honest, and competitive on his pricing. Mitch has done a number of jobs in our house, including installing a new boiler, water tank and radiators. All to a brilliant standard. I will happily recommend Mitch and Grand Union Plumbing!


Very happy with the service I have received, the service was prompt, efficient and professional. Yes, I would use again.

Clare Price

Amazing work and attention to detail and Mitch is a great person to work with

Made in Sud Pizzeria

Very friendly service. On-time and very professional. Also very careful about safety during the current COVID outbreak.

Andrew Robinson

Mitch is super friendly and professional, happy to give advice and he’s done loads of work for me.

G Man

Highly recommended, would use again

Mandi Willett

Highly recommend Mitch. Polite, professional, on time. Great service.

Susan B

Mitch replaced our boiler and ran new pipework, plus relocated some radiators. He did a brilliant job and I wouldn’t hesitate to recommend him! He was punctual, helpful and polite.

Suzanne Simmons

I had a new bathroom fitted by Mitch. He was absolutely excellent. He was polite, tidy and did an exceptional job. Reasonably priced too. 100% recommend.


Excellent service. I contacted them for a boiler repair. They responded within hours with prices. Once they confirmed part availability, they fitted within days.  Very efficient, great service and I liked their clear pricing.

Definitely recommend & I will be booking my annual service with them in future.

Well done!

Sheena Mac

Grand Union replaced our central heating system and in doing so we requested that it be relocated from the airing cupboard into the Garage.  The work was completed professionally & on time with the relocated pipework like a work of art, very neat and orderly.  I would have no issue with recommending Grand Union, and will certainly be using them for all our gas & plumbing needs.


I have called Mitch out twice since moving into our new house a month ago. Both times he has managed to fit in an appointment fairly quickly to resolve our issues. He has been professional and friendly, offering advice on other issues that I have seen. I would definitely recommend his services.

Simon Edwards

We have used Grand Union Plumbing several times as we had a really tricky fault. We found Mitch to be really excellent. Very happy to recommend, 10/10

Annette McDade

Called Mitch out on very short notice, extremely reliable and great rates, would highly recommend Grand Union Plumbing and Heating. Also provided advice with other queries aside from the job at hand- with no reluctance. Great service, thank you for your hard work and honesty Mitch.

Dushan Gnanakumar
Great service, polite, attention to detail. Would highly recommend.
Ajvinder Dhatt
Had a leak that needed fixing asap and Mitch gave me advice over the phone to deal with it until he could get to me, then came out within the hour on a weekend! Would highly recommend
Hannah Manners
Great company would highly recommend for any heating & plumbing issues
Terry Adolpho

Definitely recommend these guys. Had a job done by them and they wasted no time to get it done and made sure I was completely happy before any payments. Nowadays companies just want to rush and take your money. Big thumps up

Tevaugh Grant
We always use Grand Union for serving and any other unforseen problems. The service and professionalism is 1st class. Would definitely recommend!!
Stephanie Horne
A great company to do business with… I used them recently for an emergency with a domestic heating system which was rectified very efficiently. A second problem (some months later) and there was no decision to make, called them and they sorted it in no time with minimum fuss, mess and very reasonably priced.
Trevor Gordon

Have used Grand Union twice now. They are very quick to respond to enquiries, reasonably priced, tidy workers and very friendly. I can’t fault them. Definitely my go to guys now for any plumbing needs.
Highly recommended

Emma Verrall
Great service from Mitch. Have used a few times for boiler service, repairs and outdoor tap installation. Always very prompt service, turns up on time and reasonable prices. Would definitely recommend!
Jon Hood

I found Grand Union Plumbing through the Gas Safe Register. I had a boiler service and gas safety certificate. Mitchell was very professional and the prices were very reasonable. I would definitely recommend and use again.

Rebecca Hughes
Mitch was very helpful when fitting my new boiler – he was very fair about price and I couldn’t recommend Mitch enough. Thanks Mitch!
Reece Hussain


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