Hi All,
A bit of background. Just over a year ago I had a Megaflo unvented cylinder and Vaillant EcoTEC unvented boiler installed to replace an increasingly unreliable Gledhill Boilermate 2000. We have the hot water on a timer to come on for an hour at 6am, and then again for another hour at 6pm. As there's only two of us it provides all the hot water we need.
All was well until we returned from a two week holiday in May. During that time I had turned off heating and hot water. I turned the hot water back on, but noticed that when it had completed heating the cylinder when I turned on the hot tap there was an initial blast of much higher pressure water before it quickly returned to normal. I just assumed it was something to do with the system not being used for 2 weeks.
However, this behaviour has continued. It's most noticeable when the boiler is actively heating the cylinder and/or it's just completed heating it. Every morning when we turn on a hot tap when we get up, we get this initial higher pressure blast. Same thing in the evening. I reported it to the plumber who fitted it, and he thought it was normal behaviour and wasn't concerned.
However, last night I was outside the house around 6:30 when I noticed water was dripping from the pipe labelled in the attached picture as 1. I went inside, ran the hot water, again had the initial blast of higher pressure, went outside and the dripping had virtually stopped.
I've attached some pictures of the interior pipework. I've labelled pipe 1 where it comes into the airing cupboard. Two pipes connect to it. Pipe 2 comes from the pressure relief on the cylinder, and pipe 3 is I believe the water supply. Hopefully the pictures make sense. There is no water visible or any dampness detectable in the tundish from the cylinder on Pipe 2, so I can only assume the water is coming from Pipe 3.
Our house has 2 en-suite bathrooms. Both have mixer showers. One is a fairly new bar type mixer shower which is used daily, the other is a Mira Excel B (1996 - 2002) mixer unit that was fitted when the house was built in 2001. This en-suite is rarely used.
The plumber came round today to investigate. When he saw the Mira shower he said he thinks this is the cause of the problem. He thinks it's allowing cold water to "backfill" into the hot water system and hence causing a pressure build up, which is why Pipe 3 is sending water outside. He commented this type of mixer unit can be bad for this. I've contacted Mira to ask their advice.
There is no easy way to isolate or remove the Mira shower unit. As far as I can tell there are no valves to isolate either the hot or cold feed. Additionally to remove it will mean trying to cut away at some of the tiling, which won't be easy. So this leaves my only option of replacing the cartridge. But at £130 I'm a little reluctant to do it. Similarly, I don't want to mess around with the tiling, make a mess and end up having to retile the entire thing. Especially if it turns out the Mira unit wasn't at fault.
I'd read a few posts about recharging the air bubble in the Megaflo, but from what I've read the symptoms of this needing to be done often involve water dripping from the pressure relief, so would be visible in the tundish. But this is completely dry.
To be honest I don't understand the mechanics of how cold water, backfilling into the hot water system could cause this.
Apologies for the long, rambling post... but any help/advice here would be much appreciated.
Many Thanks...
A bit of background. Just over a year ago I had a Megaflo unvented cylinder and Vaillant EcoTEC unvented boiler installed to replace an increasingly unreliable Gledhill Boilermate 2000. We have the hot water on a timer to come on for an hour at 6am, and then again for another hour at 6pm. As there's only two of us it provides all the hot water we need.
All was well until we returned from a two week holiday in May. During that time I had turned off heating and hot water. I turned the hot water back on, but noticed that when it had completed heating the cylinder when I turned on the hot tap there was an initial blast of much higher pressure water before it quickly returned to normal. I just assumed it was something to do with the system not being used for 2 weeks.
However, this behaviour has continued. It's most noticeable when the boiler is actively heating the cylinder and/or it's just completed heating it. Every morning when we turn on a hot tap when we get up, we get this initial higher pressure blast. Same thing in the evening. I reported it to the plumber who fitted it, and he thought it was normal behaviour and wasn't concerned.
However, last night I was outside the house around 6:30 when I noticed water was dripping from the pipe labelled in the attached picture as 1. I went inside, ran the hot water, again had the initial blast of higher pressure, went outside and the dripping had virtually stopped.
I've attached some pictures of the interior pipework. I've labelled pipe 1 where it comes into the airing cupboard. Two pipes connect to it. Pipe 2 comes from the pressure relief on the cylinder, and pipe 3 is I believe the water supply. Hopefully the pictures make sense. There is no water visible or any dampness detectable in the tundish from the cylinder on Pipe 2, so I can only assume the water is coming from Pipe 3.
Our house has 2 en-suite bathrooms. Both have mixer showers. One is a fairly new bar type mixer shower which is used daily, the other is a Mira Excel B (1996 - 2002) mixer unit that was fitted when the house was built in 2001. This en-suite is rarely used.
The plumber came round today to investigate. When he saw the Mira shower he said he thinks this is the cause of the problem. He thinks it's allowing cold water to "backfill" into the hot water system and hence causing a pressure build up, which is why Pipe 3 is sending water outside. He commented this type of mixer unit can be bad for this. I've contacted Mira to ask their advice.
There is no easy way to isolate or remove the Mira shower unit. As far as I can tell there are no valves to isolate either the hot or cold feed. Additionally to remove it will mean trying to cut away at some of the tiling, which won't be easy. So this leaves my only option of replacing the cartridge. But at £130 I'm a little reluctant to do it. Similarly, I don't want to mess around with the tiling, make a mess and end up having to retile the entire thing. Especially if it turns out the Mira unit wasn't at fault.
I'd read a few posts about recharging the air bubble in the Megaflo, but from what I've read the symptoms of this needing to be done often involve water dripping from the pressure relief, so would be visible in the tundish. But this is completely dry.
To be honest I don't understand the mechanics of how cold water, backfilling into the hot water system could cause this.
Apologies for the long, rambling post... but any help/advice here would be much appreciated.
Many Thanks...
