Megaflo UVC - Very Loud Noise When Hot Tap Opened

[techweb]

Hi,

I have noticed that when a hot tap is opened for the first time after a heating cycle (in this case a bath tap), the water flows for a couple of seconds and then there is a very loud noise as can be heard in the video.

Any ideas what it may be? I couldn't deduce the source. The EV was recently checked and pressure increased from 1 to 3 bar per instructions but notably it did this before. I just at that time didn't know the trigger. It hasn't always done this however, probably the last couple of months or so.

Thank you.

 

[techweb]

I'm going to ask my plumber tomorrow but I suspect the PRV on the cold inlet side...

 

[ShaunCorbs]

Internal baffle

 

[techweb]

Internal baffle

My internal baffle was confirmed by Baxi as disintegrated and now have an external EV which was checked recently and increased pressure from 1 to 3 bar per instructions. It did this noise before the EV pressure change.

 

[ShaunCorbs]

My internal baffle was confirmed by Baxi as disintegrated and now have an external EV which was checked recently and increased pressure from 1 to 3 bar per instructions. It did this noise before the EV pressure change.

They would normally supply you with a brand new cylinder as when it degrades it breaks off and can clog stuff so defo shouldn’t be used once identified

 

[techweb]

They would normally supply you with a brand new cylinder as when it degrades it breaks off and can clog stuff so defo shouldn’t be used once identified

They stopped doing that and now fit an EV and strainer. My plumber already put an EV on years ago and I declined the strainer for obvious reasons as it will just get clogged.

Been like it for years. I noticed the bits appearing on kitchen tap mesh but that’s the only tap with mesh in our house. The shower mixes fortunately don’t have them. Most of it has probably worked its way out.

It was only a few weeks ago I contacted Baxi as had no idea on the warranty. They sent an engineer out and he was frank. Strainer a waste of time and that baxi have changed their policy. He did confirm that the cylinder install was very good but at that time I didn’t know what triggered the noise as I would have asked him.

 

[ShaunCorbs]

Well that’s strange as they’ve supplied me one recently I would push more and state there liable for showers and taps as there blocking up also you shouldn’t drink the tap water

 

[techweb]

Well that’s strange as they’ve supplied me one recently I would push more and state there liable for showers and taps as there blocking up also you shouldn’t drink the tap water

To be honest I usually would but I couldn’t replace it without dropping the ceiling. It’s in the loft and must have been fitted before they went in. No way a cylinder would go through the hatch.

In terms of this issue, I’ll see what my plumber says but with the EV being OK, I think it’s got to be either the PRV on inlet or the fill valve.

 

[ShaunCorbs]

Or the diaphragm banging around

 

[techweb]

For completeness, attaching pictures of the installation. I have been told by my plumber and baxi the likely cause is the water inlet control block / PRV. I will be getting this changed shortly.

 

[John.g]

To be honest I usually would but I couldn’t replace it without dropping the ceiling. It’s in the loft and must have been fitted before they went in. No way a cylinder would go through the hatch.

In terms of this issue, I’ll see what my plumber says but with the EV being OK, I think it’s got to be either the PRV on inlet or the fill valve.

If not allready installed, you might ask your plumber to supply and install a pressure gauge on the PRV outlet which should/might have a tapping for it, it would be quite useful for trouble shooting even though it won't give the cylinder pressure after reheating, normally, the EV is sized to 10% of the cylinder capacity so even if the whole cylinder is reheated to 65C, the final pressure should still only rise to 3.9bar, hardly likely to cause any problems when the hot tap is opened, if the PRV is leaking past then the pressure only has to rise to 4.2bar to give a cylinder pressure of 5.8bar on reheating which may cause that noise, even though it shouldn't, on opening the hot tap.
You might just post tne cylinder volume and the EV volume, should be labelled on both.

 

[techweb]

If not allready installed, you might ask your plumber to supply and install a pressure gauge on the PRV outlet which should/might have a tapping for it, it would be quite useful for trouble shooting even though it won't give the cylinder pressure after reheating, normally, the EV is sized to 10% of the cylinder capacity so even if the whole cylinder is reheated to 65C, the final pressure should still only rise to 3.9bar, hardly likely to cause any problems when the hot tap is opened, if the PRV is leaking past then the pressure only has to rise to 4.2bar to give a cylinder pressure of 5.8bar on reheating which may cause that noise, even though it shouldn't, on opening the hot tap.
You might just post tne cylinder volume and the EV volume, should be labelled on both.

Thanks...

So I am doing away with the Calefe PRV block as technically this is not the correct part as technical at Baxi told me. I have ordered the correct parts and my plumber will fit them. Both my plumber and Baxi believe this to be related to the PRV.

Interesting point you mention re the pressure increase.

The cylinder is 210L capacity and it's an 18L EV. This is correct per their sizing charts.