Boiler pressure low repeatedly

velvetti

Hi All,
We've recently bought our first home and replaced the old boiler with a new combi one. Previous boiler was a conventional (hot cylinder in wardrobe upstairs, cold tank in loft). New one is a combi:  Worcester Bosch Greenstar 1000 (24 kW), installed in Nov 2024.
Since end of December, we have noticed that the boiler stops working intermittently and shows a 'low pressure'  sign on the display. It is easily fixed by repressurising the boiler using a pair of valves. This has been happening quite regularly over the last couple of months, almost once every week and I'm wondering if this is due to a faulty installation or whether there is a leek in the central heating system. We got the boiler installer to visit and he asked us to monitor the situation for anotehr month. He also suggested we may have to inject some sealant fluid into the central heating system which would seal any leaks. 
Is there a better way of locating and fixing this issue? 
This may or may not be relevant: whenever central-heating water flows into the radiators, we hear a lot of tingling of sounds. I suspect it;s due to debris in the central heating system but I'm not sure. 
Thanks in advance for any help

FreeBear

Do any of the pipes run under a concrete floor ?

If so, there is a very good chance that they have corroded. A thermal imaging camera would show where the pipes run and might even reveal if the are leaking. If not lift the flooring to see if there are any wet patches.

Albermarle

I presume you have gone from a heating system that was only under the pressure from gravity from the cold tank , to one that is under mains pressure. 
The higher pressure may have found a weak spot in the heating pipework.

TELLIT01

Putting sealant into the system may well stop any small, pinhole or minor joint leaks.  That was done when we went from gravity feed to closed system.  We've had no leaks to date (touch wood)

velvetti

We’ve got concrete floor only in the kitchen and I don’t think any pipes run under it.
Regarding your suggestion, it sounds like quite a major task. I guess if there’s no other way then we’ll have to do it but I’m really hoping there’s something quicker that we could try. 

Thanks anyway.

Ectophile

There will be a pressure releif valve in the boiler.  the pipe for that usually pokes out through an external wall.  Check that it diesn't drip when the boiler is running.  If it is dripping, then that valve has failed.  The pressure relief valve pipe is not the condensate pipe.  The condensate pipe is supposed to drip.

Otherwise, one way or another, you have a leak.  The tricky bit may be finding that leak.  Start off by having a close look at the ends of the radiators.

Vortigern

Easiest leaks to find and fix are at the radiators. Check for watermarks on floorboards,  carpets and floor coverings. Tie some toilet tissue around the pipes, leave for a few days and check for dampness.

Also check the pressure relief valve's discharge pipe. This is normally a short copper pipe on an outside wall with its end turned in towards the wall. You should not see any leakage from this pipe.

The "tingling" sound could be air bubbles circulating with the water.

Beeblebr0x

Running the risk of creating a leak was the reason my plumber was reluctant to change my conventional system for a combi.

How good are the leak sealants mentioned by velvetti?

ThisIsWeird

Hi Velvetti.
Do you know what checks your plumber carried out?
I'd hope it would have included a good visual inspection of the rads and valves? 
And the safety discharge pipe mentioned by Vorti above. This pipe will be a new addition to your install, so should be obvious. Check the end outside - it should be bone dry. Is it?
If wet from rain, you can try rubber-banding a wee clear plastic bag over the end, to see if it catches any discharge.
Sealants presumably work, but I'd only want it used as a last resort.

JohnB47

Wouldn't a competent plumber/installer have some sort of kit to pressurise the pipework and rads (with the boiler isolated) and therefore confirm if the pressure drop is outside or inside of the boiler?

ThisIsWeird

JohnB47 said:

Wouldn't a competent plumber/installer have some sort of kit to pressurise the pipework and rads (with the boiler isolated) and therefore confirm if the pressure drop is outside or inside of the boiler?

The simple way to do this, tho' not really convenient at this time of year as heating is required, is to repressurise, and then isolate the boiler from the CH using the valves on the flow and return pipes under the boiler.
Leave it for as long as the pressure drop would usually be noticed, and then check the reading. A drop means a loss from within the boiler. No drop, but a fall as soon as one valve is reopened, indicates a leak in the rad/pipework. 
For the latter scenario, if no visible sign of a leak - Ie it's taking place under the floor - then I'd consider sealant.