Vaillant Cracked Sump

16 Apr 2024
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United Kingdom
Hi Guys,

Just had a boiler pressure drop identified in our Vaillant Ecotech plus 618 with a leak from a crack in the 'sump' (his words). Looking online I can only see whole heat exchangers to resolve the issue as opposed to a smaller and cheaper part. Photo shows crack where the red circle is - it seems to be made of plastic as opposed to metal - and seems to be bolted to the heat exchanger. Can you get this part on its own? As the heat exchanger is around £500. Any help appreciated.


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I guess you'd really call it a manifold. It's the transition from the flow/return pipework to the tube bundles inside.
Sometimes heavy handed repairs result in the pipe spigots cracking..I'm not aware of cracking in that area bit others may have seen it.
Not repairable so new heat exchanger/boiler time.
Don't be fooled by refurbished heat exchangers...due to the parallel tube design they can't be cleaned properly.
I had to replace the heat exchanger, so I dismantled it to find out the cause of the leak, those parts are siliconed together, you will damage them when separating them in my opinion. I found a large pinhole on the inner face of one of the "stainless" loops that make the heatexchanger work, cheap nickel free stainless I think it is made of.
Our 11 year old Vaillant boiler failed at exactly the same place. water was leaking from the join.
The replacement cost was so high (quoted around £750 for the part) I opted for a new boiler but kept the old one to dismantle.
The parts are joined together but it's not silicone - it's some sort of red coloured hard resin.
To get them apart was impossible. I ended up using a hammer and chisel .... you can imagine the result. Lots of wee chips of glass reinforced plastic.
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Is the boiler within the guarantee period?

If not, you might be able to take out Vaillant's Repair and Care plan and get the heat exchanger replaced by Vaillant for £420. There is also a Fixed Price Repair, but I don't think that covers heat exchangers. Maybe ring Vaillant to discuss options.

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the red resin is red hermetite I think, and I used a hacksaw to get mine apart.

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