Potterton Puma 80 - no hot water - again

The pilot light went out a couple of weeks ago. Could reingnite it, but it didn't flare when the hot tap was turned on. No hot water :-(. There was also a leak coming from the left side of the unit. The low pressure light was also lit. We called a plumber, he fixed it and said we needed a new pump. He still hasn't come back to fix it yet.
Anyway...the hotwater is not working again - no leak this time. No low pressure light. The boiler seems to flare, then for a second a trickle of hot water, then just cold very low pressure water. I've spoken with another plumber and he reckons it needs a descale, based on the fact that the pressure is so low. He hasn't seen the boiler yet. Could this be the problem? I've read in other threads that "descaling" is something plumbers throw in to make more money.
Any opinions??
Lesley
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

If you want to test the low pressure sensor, remove it's connector on the pcb. (Open circuit means the pressure is OK, short circuit means low pressure). It is prone to getting crud in it which prevents it from working properly
If the heat exchanger is scaled up, it will get hot very quickly as there's not enough water flowing through it to carry the heat away, the trickle and low pressure hot water would add weight to this. How long does the boiler fire up for?
--
geoff

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Where in the country do you live?
It could well be scaling up, as he suggests.
Christian.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.