Hot water boiler pressure

Posted by: Fisbey on 03 February 2006

I am losing pressure on my combination boiler - it drops from 1.5 to 1.2 in less than a week - which means I have to 'top it up' every week. I also suffer from the hot water from not being particularly hot.
A friend (corgi registered etc) installe dthe whole heating/hot water system including the boiler about 3 years ago and has 'fiddled' with it, but I still have problems.
I can see no sign of water loss (through the ceilings) - would it be prudent to check under the downstairs floorboards? There is no sign of water loss from the outside 'overflow.
Are ther eany other causes of pressure loss?

Any advice/ideas?

Thanks
Posted on: 03 February 2006 by lyndon
hi
your pressure fluctuations are quite normal, the 2 pressure readings you took, were they at the same temperature, as you have a closed system the pressure will fluctuate. also if the system is new you will have some air left in it, presumably there is an aav on the boiler itself so as the the system rids itself of the air the static pressure will reduce, this can take a few weeks.
if the dhws is cold then try, 1. do you have a hot water temperature adjustment ?
or as i have done reduce the cold water inlet pressure, there will be a valve on the cold feed on the inlet to the boiler regulate this whilst running the bath tap until the water is hot enough.

lyndon

btw i am an hvac engineer
Posted on: 03 February 2006 by Fisbey
OK thanks - I have turned down the pressure, maybe I need to turn it down more Confused

I think I'll have to monitor the readings and ensure I take readings at the same time of day - it was very low this morning but the boiler would have been stone cold - so I'll check it in a week or two under the same conditions.

There is no visible adjustment of the water temperature and the system is all 3years old.

I keep a check and report back!
Posted on: 03 February 2006 by nicnaim
Sounds like you have got a leak in the system somewhere. When my combi boiler was fitted a couple of years ago the plumber explained that only a relatively small amount of water needed to leak out to cause a drop in pressure. About a cup full was his description. Sure enough when experiencing a similar drop in pressure, it was eventually traced to a leaky radiator behind a settee. The amount lost was not causing any puddles or staining the ceiling below, and was barely noticeable.

Nic
Posted on: 03 February 2006 by Don Atkinson
A pressurised system should retain its pressure at a rock-steady value during the typical diurnal temerature variations we experience in the UK.

I fit doesn't, there is a leak somewhere.

However, the leak could be slow enough for the water to evaporate before it makes its presence known or before it can cause serious damage. However.....

Just before Xmas, my system was dropping from 2.0 bar to about 1.4 or 1.6 bar every copule of days. Over a two week period I couldn't find the leak. Eventually, the parquet floor in one of the bedrooms heaved overnight, and revealed the slight leak from an adjacent pipe/radiator valve. Water had been seeping/evaporating but nevertheless soaking into the floor.

Less than 5 minutes with a spanner to fix the leak.

Over £1,000 (insurance) to replace the parquet floor.

Cheers

Don