air getting into hot water system

Andy From Sligo

Not long moved into house, its an old house built in 70s'/80's. When i run hot water for a bath it fills up bath but towards the end starts spluttering. After a bath and when the header tank up in the loft is filled up, if I run the basin tap that splutters for a while. I am thinking that the bath is depleting the header tank quicker than it is being filled up from the ballcock valve and sucking in air from the bottom of the header tank in the loft - could i be right? .. although when I am running the bath I can hear the header tank up in the loft fill up (its above the bathroom) and it sounds quite powerful enough the water going into it. is there anything else that could be happening? just one of those niggling things i would like to get sorted out if i can one day.

Sir Arthur Daley

My sisters house had the same problem, i increased the capacity by installing a second tank in parallel.

Andy From Sligo

Sir Arthur Daley wrote: »

My sisters house had the same problem, i increased the capacity by installing a second tank in parallel.

thanks, good idea there - but you have also given me another one, maybe the present tank isnt filling up high enough at the top, i normally set the ballcock on these tanks to a little under the overflow tapping. i must have a look next time im up there and see if its filling up to a high enough level before the valve shuts off, the person who put it in might not have set the water level high enough.

Sir Arthur Daley

In my sisters house it was down to the incoming mains, it is coming from a spring in the mountain country style and pressure was not fantastic. The second tank cured it anyway.

2 stroke

I had a similar problem that baffled me for more than a year.
The problem was that lime had built up and nearly blocked the hot water pipe rising out of the cylinder, the flow from the cylinder couldnt keep up with the draw to the taps, meaning that the level in the expansion pipe fell and air was been drawn down the expansion pipe.
I replaced about 3 feet of 22mm pipe which had narrowed to about 5mm and had to drill down through the lime in the cylinder. Btw, removing the pipe from the cylinder wasn't easy. The lime was solid rock, holding everything together after I opened the compression fittings. Would have been a good time to change the cylinder but I tackled this job on a bh weekend.

Andy From Sligo

2 stroke wrote: »

I had a similar problem that baffled me for more than a year.
The problem was that lime had built up and nearly blocked the hot water pipe rising out of the cylinder, the flow from the cylinder couldnt keep up with the draw to the taps, meaning that the level in the expansion pipe fell and air was been drawn down the expansion pipe.
I replaced about 3 feet of 22mm pipe which had narrowed to about 5mm and had to drill down through the lime in the cylinder. Btw, removing the pipe from the cylinder wasn't easy. The lime was solid rock, holding everything together after I opened the compression fittings. Would have been a good time to change the cylinder but I tackled this job on a bh weekend.

Thanks for that, both the hot water taps and the cold water taps (from header tank in loft) seem to be same pressure (low!) so if there was limescale blocking pipe on pipe from copper heating cylinder wouldnt the hot water taps have less pressure on them than the cold water taps?

Sleeper12

Your attic tank is running dry / not filling fast enough. There is nothing else can cause this.
The ballcock might need to be changed or the mains water pressure is bad. If the mains water pressure is bad then you may have a leak in the driveway. With water meters coming in you should keep an eye on it.

II it's just bad pressure & no leaks then you need to install a 2nd attic tank. Try the ballcock first. They cost less than €10 & it's a job you could do yourself if you are any way handy

2 stroke

Andy From Sligo wrote: »

Thanks for that, both the hot water taps and the cold water taps (from header tank in loft) seem to be same pressure (low!) so if there was limescale blocking pipe on pipe from copper heating cylinder wouldnt the hot water taps have less pressure on them than the cold water taps?

Presure is the same as both taps have the same head, try temporarily sealing the expansion pipe with insulating tape or similar (careful now, expansion pipe is there for a reason) and see if it still happens.