Hot water pipe keeps bursting (2 kids and no heating in November)

[tobiasuk]

Hello everyone, I'm not a plumber, but I'm having an issue which keeps re-occurring and the engineers coming out to us do not seem to know why. So here is the story.

We have a pressurised system. When our boiler was serviced, the engineer had to abort the service as he found the following:

• Boiler kept on starting, then shutting down due to overheating
• Heat Exchanger was showing ripples, probably due to overheating.

The engineer pointed out this is likely due to sludge/dirt in the system. Our Worchester boiler is 7 years old. We got a new
heat exchanger from Worchester and then had a heating company do the following:

• Replace heat exchanger
• Power flush system
• Install MagnaClean filter
• Replace water pump (advised due to age)

After that the boiler seemed to work fine again and we had it serviced without issues.

10 days later we came back from a week of holiday. During our holiday the system was in holiday mode, keeping the temperature above 10 degrees.
The day after our return the hot water return pipe to the boiler burst. It was a plastic PB pipe that burst (not at a joint).
The burst happened fairly close to the boiler, where the plastic pipe transitions into copper pipe. The engineer was unable to
say why the pipe had burst so just ended up replacing the burst part with new plastic pipe. The old pipe was not showing
any visible signs of weakness, fitted correctly and was the correct part - we were told.

About 2 weeks later the new plastic pipe burst again - in exactly the same place! Another company came out and could not find the root cause either.
From what I remember they checked the following:

• Relief valve
• Magnetic filter
• Some other things that unfortunately I can't quite remember

He ended up replacing the broken plastic pipe with a slightly longer copper pipe.

It's almost December now and we live in constant worry that we will have another burst soon, as there seems to be an underlying issue.
We have a baby and a toddler, so having no central heating isn't much fun. The thing is - according to both engineers - there isn't
anything else they could do to find the fault - other than start opening walls and floors and check every single pipe. Argh!

Oh and just to add:

• The bursts happened in November. I've check the weather history and it was not nearly cold enough for water to freeze (just saying).
• I have attached a photo of the pipe that burst first. The engineer said the scratches were probably cause by him removing it.

So I was wondering if people might have ideas what to check in case this happens again, before we start opening walls.

Thanks in advance guys
Tobias

 

[ShaunCorbs]

How close is it to the boiler as it looks heat damaged ?

 

[tobiasuk]

How close is it to the boiler as it looks heat damaged in

Maybe 40-50 cm above the boiler with the boiler being about 30 cm underneath the ceiling. The white plastic pipe on the photo in the ceiling was the replacement pipe.

 

[ShaunCorbs]

Need to be a minimum of a 1.5m away eg need to have 1.5m of copper

Also the pipe on the right looks very kinked on the joist ?

 

[Chuck]

It's interesting that it's the return pipe, which is cooler, as opposed to the flow pipe

Difficult to be sure from the photos, but the bend radii all look a bit small to me. As a rule of thumb, the curve radius should be at least 10 times the pipe diameter. (Check the manufacturer's specifications for the exact values.)

Is the failing pipe rubbing against a snag, e.g. the tip of a screw that's been driven into the joist?

 

[oz-plumber]

Send a pic of the pipe to the manufacturer.
They may shed some light on the situation.

 

[tobiasuk]

Adding some more photos from after the second pipe replacement.

Also the engineer did mention there should be 1m copper from the boiler but said it might be from the boiler pipe connectors at the bottom of the boiler rather than the top of the boiler. Hm.

 

[tobiasuk]

Failing pipe

It's interesting that it's the return pipe, which is cooler, as opposed to the flow pipe

Difficult to be sure from the photos, but the bend radii all look a bit small to me. As a rule of thumb, the curve radius should be at least 10 times the pipe diameter. (Check the manufacturer's specifications for the exact values.)

Is the failing pipe rubbing against a snag, e.g. the tip of a screw that's been driven into the joist?

The failing pipe was not touching anything other than the joist through which it went.

 

[tobiasuk]

Need to be a minimum of a 1.5m away eg need to have 1.5m of copper

Also the pipe on the right looks very kinked on the joist ?

It is a different pipe but yes it does look quite kinked - I'll take a closer look when I have time later today.

 

[Last Plumber]

It looks too close to the boiler for plastic as above.
The bend is too tight.
Plastic expands and contracts around 1% so it will move about a fair bit and soften and harden.
I would say it needs taking out and re-installing better and in copper.

 

[tobiasuk]

It looks too close to the boiler for plastic as above.
The bend is too tight.
Plastic expands and contracts around 1% so it will move about a fair bit and soften and harden.
I would say it needs taking out and re-installing better and in copper.

I think we may just have that done then. Although this pipe has been in the house long before we moved in (about 3 years ago). So it has been working fine up until we had some work done. So we are wondering what could possibly have changed so that it keeps on bursting now, when it was fine before.

 

[tobiasuk]

Spoke to the pipe manufacturer and showed them the photo. They said it looks like a temperature burst potentially caused by an airlock. But that would only explain the first burst and not the second one they said. They didn’t know how the second burst could be explained. Does an airlock sound likely? The company who did the power flash did bleed all radiators afterwards. Or at least they claimed that they did.

 

[ShaunCorbs]

How long were they there ?

 

[Last Plumber]

Spoke to the pipe manufacturer and showed them the photo. They said it looks like a temperature burst potentially caused by an airlock. But that would only explain the first burst and not the second one they said. They didn’t know how the second burst could be explained. Does an airlock sound likely? The company who did the power flash did bleed all radiators afterwards. Or at least they claimed that they did.

I could understand an air lock leading to that if the heat that softened or melted it was external or maybe if steam were generated inside the pipe?

 

[Deleted member 120897]

The pipe might be rubbing on the joist, which looks rough cut

 

[oz-plumber]

Why don't you find out when the system was installed and how long the pipe warranty is.

If it failed within the warranty - claim the damage and repairs off the manufacturer.

They may take some more interest in the situation if they know they are liable for the repairs.
As for the airlock excuse - I don't buy into that one ....twice.