Project Description

Worcester Bosch Heat Only Boiler Replacement

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This project was for a straight swap, as they say in the trade, which meant the boiler was to be replaced but kept in the same location. However, that didn’t mean it was necessarily a quick and easy job.

The old boiler had been condemned, so they needed a new one fitted quickly to get their heating up and running. But there were a few things that we needed to consider:

  • The existing flue hole was in the right place, but…

  • They were going to need a new 22mm gas supply.

  • The customer specifically wanted a Worcester Bosch boiler.

  • With this system, the heating works from a thermal store.

Why did they choose Grand Union Plumbing & Heating?

When someone speaks to one of our gas safe registered engineers, they instantly know they’re talking to someone with knowledge and experience. So when we get calls about replacing a boiler, we find people get peace of mind that they’re dealing with professionals very quickly. We also understood why they were keen to install a new Worcester Bosch boiler – for they are known for their reliability. Our quest, however, was to locate one…

Our new boiler replacement process for this project

The customer’s existing system worked from a boilermate thermal store. This meant the system had to be drained down completely, which took longer than usual because of the time taken to drain down the radiator pipework; it’s just one of those things. However, that was not all that was of note for this project.

The existing installation had been wired incorrectly, which meant that the central heating pump had been constantly running. Thus we needed to rewire this to prevent the new pump from failing prematurely in the future.

We also needed to fit a new 22mm gas supply from under the stairs, and route it through to the utility room. And run a condensate pipe into the utility room sink drainage.

We then added inhibitor back into the system to prolong the life of the new setup, bled the radiators, commissioned the new system, and registered the boiler with the manufacturer. And we wired the new boiler into the existing heating controls.

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The benefits of our solution

Our knowledgeable team of gas safe registered engineers are very good at spotting problems early on. So they were able to rectify the incorrect wiring setup of the pump and ensure the new one could enjoy a longer lifespan.

They were also able to fit the new 22mm gas supply without causing disruption, and run the condensate pipe into the utility room sink without making a mess.

It’s always our approach to leave a newly installed system with the best chance of operating as long as possible, so adding inhibitor back into a system is just part of our standard new boiler replacement process.

In a nutshell:

  • Our experienced heating and plumbing engineers can spot and rectify problems quickly.

  • We were happy to source the exact boiler make and model the customer desired.

  • We made it look like a straight swap… when it really wasn’t; but that’s how we like to work.

After care

Our policy is to ensure there is a full handover whenever we install a new boiler. Thus we:

  • Explained the differences between the old system and the new one.

  • Took the customer through how the new system works.

  • Demonstrated that the existing heating controls operated well with the new system.

We also took the old boiler and all packaging away to be disposed of in an environmentally friendly way.

Did we go the extra mile?

Oh indeed we did… all the way to Luton… because that was where we tracked down the exact boiler make and model the customer desired.

Need to replace your boiler?

If you’re looking to replace your existing boiler with a new system and you have a particular one in mind, please don’t hesitate to give us a ring on 01908 034194. We’ll do what we can to find exactly what you’re looking for and get it installed.

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Areas we cover

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

I’ve used Grand Union 3 times and every time the service is excellent and the price very reasonable. Engineers are very good at letting you know what they are doing and there are no hidden charges. They even managed to do a job at short notice. They work tidily and even followed up with a message to check my heating was still ok the following day. Highly recommend

Claire Edwards

Excellent service from Mitch!
Responsive, courteous and informative.
Work swiftly done too, with clear explanations throughout.
Thanks again, Mitch.

Used grand Union plumbing to service my boiler and couldn’t of asked for a better service. They were on time and actioned the job in a clean and professional manner. Very nice to see they were operating in a covid secure manner without being promoted too

100% will be used again in the future

Tom Holland
Highly recommend Grand Union Plumbing & Heating. We called Mitch after getting nowhere with the first 2 heating engineers we contacted. In contrast to them, Mitch quickly diagnosed the fault, ordered the part and replaced. Totally professional and good value for money.
Mike Kennedy
I found Grand Union on local heroes. Id given up on British gas and NPower/homeserve.
Mitch was honest from the get go. Came round and gave me quote got the worl done within a couple of days once parts came.
Very highly professional. Very friendly. Perfect on time. Clean. Safe. What else can I say. I will be using only Grand Union here on and cannot recommend enough.
Amazing service Mitch Andy and Cory all amazing guys came out Xmas Eve went above and beyond to get me sorted and were amazing with my children letting them watch and so polite couldn’t recommend highly enough 10/10
Steaves Jen
Highly recommend the team to fix any plumbing or heating issues. They arrived as scheduled and it was great to have such a high standard of service. Will definitely be my contact for anymore plumbing issues and for boiler services.
Owen Thomas
Contacted them after having three boiler services being cancelled by a Big Five company only resulting to a wait till May for the 4th appointment. From the first day I contacted them Andy came around in a week’s time and provided excellent customer service and serviced our boiler very efficiently and quickly. The appointment ran a bit late due to another emergency call but both Mitch and Andy were apologetic and polite. Appreciate there excellent customer service on top of a job done well. Will be calling on them in future again for sure. Thank you.
Kaanita Khan
Would highly recommend Grand Union plumbing, really knowledgeable team. They were able to identify the problem with our heating pressure gauge, and release valve really quickly and stop our leak straight away. Thanks
Emma Thompson
Love these guys, have been using them for years and will keep using them for years in the future. They’re helpful, do amazing work each and every time, and are respectful of your home, both Andy and Cory took their shoes off when they came into the house recently, Cory put down dust sheets when he was fitting my new radiator in the bathroom (tiled floor wipes clean, but still put it down).
100% recommend them for any and all plumbing works and looking forward to having them do more work for me later in the year.
Ian Kockelbergh

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!


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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