Blocked plate heat exchanger: heating waterway or mains waterway?

[stequin]

Hoping someone can help diagnose whether the blocked plate head exchanger in my mum’s combi boiler is down to the heating waterway or mains waterway.

Issue is that she only gets around a basin’s worth of hot water before the tap runs cold. No issue with water pressure from tap, and central heating unaffected.

She’s now had visits from two plumbers, who both diagnosed the issue as a blocked plate heat exchanger and flushed it out. This fixes the problem for around a month, so seems to be the cause.

The problem is now back so it seems she needs to deal with the underlying cause of the blockage. Based on what I’ve read it seems to me the issue is sludge in the central heating system blocking the heating waterway that needs a power flush to sort.

However, my mum is fairly sure the second plumber told her the issue is with the quality of mains water coming in e.g. due to nearby building works. This doesn’t make sense to me as I’d expect a reduced flow of water if the mains waterway were blocked, rather than a dropoff in temperature. She’s also not had any issues with the mains water over the past few months. Questions are, therefore -

• Am I correct that the mains supply issue doesn’t make sense?
• If the issue is with the heating waterway, is a powerflush the most realistic solution?
• What on earth is the fix if the issue is with the mains?!

Any input appreciated – realise that the easiest way of confirming which waterway is blocked would be to get the plate heat exchanger out and look, but a) she lives 250 miles away and b) could really do with avoiding the expense of a third callout, especially if a power flush is needed…

 

[townfanjon]

When a hot tap is run for a few minutes, what happens to the boiler display, does it rise in temp and then stop for a few minutes and rise again .
It could also be a part in the boiler , a shower valve or mixer tap “passing” . Any idea who the manufacturer is ?

 

[centralheatking]

What boiler make and model ? If the central heating is good then very unlikely the hex cause most boilers share the hex. but we need
make and model. centralheatking

 

[stequin]

Thanks - it's a Worcester Bosch Greenstar 30i.

 

[centralheatking]

Ok that has one shared hex so its not the hex if the heating side performs. Experts here will advise about weather compensation
or it might be the diverter...wait till they wake up and see what the collective wisdom says...bearing in mind you dwell quite a distance from your mothers gaff. centralheatking

 

[Aire]

If it's blocking up within a month it's likely caused by the heating water, and also if the plumbers are only cleaning the heat ex by running it under the tap, it's not going to fully clear the problem. Has any engineer mentioned the quality of the heating water or performed a flush on the heating system. Do you have a system filter installed?

 

[Millsy 82]

I'm not a big fan of cleaning out plates, you will never get them back 100% and if they block up in the future customers want the work done for free. So to me if blocked plate replace it.

The problem you have to work out though is why has it blocked? If its dirty water powerflush fit system filter and then replace, if it is muck coming through the mains then get onto you water provider and possibly fit a strainer before the boiler to catch it. They may then foot the bill if its mucky mains.

Cleaning/ replacing a heat exchanger with out sorting the main cause of the issue is a bit pointless.

 

[stequin]

Thanks all. Neither of the engineers mentioned the quality of the quality of the water or performed a flush of the system - no filter installed either. What can we expect a reasonable price to be for a flush/filter/replacement plate?

Also interested to hear that dirty mains water could indeed be the culprit - in this case would you really see the water pressure coming through the tap unchanged? Any idea how much grief we can expect getting the water provider (United Utilities) to look into/acknowledge the problem?

 

[Aire]

I'm not saying the issue isn't with your mains but nearby building work shouldn't affect the quality of your water. If the water was dirty due to the building work, you would end up with tap filters and toilet inlets blocking and if you filled a glass of water and let it stand, you would see the deposits settle at the bottom.
If your system doesn't have a filter and hasn't been flushed then that is the likely culprit. For a proper power flush, filter and new plate id expect prices around the £1k mark.

 

[stequin]

Thanks - from the above it seems like heat ex most likely culprit, but (predictably) only way of confirming for sure is to get an engineer out! Shall recommend that course of action...

 

[centralheatking]

Unmaintained ch systems are a nightmare to pin down..just get
it flushed out, fit a mag filter and get it guaranteed...if its your old mum...just do BG at least they will take your money but be available just like that and its on the drip...ie monthly payment
centralheatking