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Shower Water Hammer


steveoelliott

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5 hours ago, steveoelliott said:

Sorry, so the Megaflow HE has an internal expansion baffle / vessel. It is apparently common for these to breakdown.

Nope. 
It’s either got an EV screwed to the top of the cylinder, and the external factory case of the UVC extends up to hide it, or it’s a bubble top where the hot pipe is extended down from the top to allow a pocket of air to be trapped to use as expansion. 

If the bubble top has depleted, you simply drain the UVC and refill  to replenish the bubble or it’s the other type and the dead EV needs to be replaced immediately. 
If you leave the ruptured factory EV in service you’ll eventually have a full and catastrophic failure and a flooded house to boot. The internal steel body of the EV ( if it’s not the bubble top gone ) rusts away day by day, exacerbated by the constant heat and influx of fresh oxygenated water, and perforated. At that stage the cold mains pressure is free to escape and flood your house. For good measure, that usually blows whilst you are out of the house and the cold mains is constant so it keeps pouring out until you arrive home…….

 

It doesn’t sound like your plumber is very experienced in UVC installs / repair I’m afraid. He may be a good general plumber, but this is a terribly dangerous scenario if the factory EV has failed, or a bloody expensive unnecessary repair if it’s just the bubble that needed regenerating.

 

Have a look to see if the lid of the UVC comes off, easily, and you’ll have your answer. 

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5 hours ago, Nickfromwales said:

Nope. 
It’s either got an EV screwed to the top of the cylinder, and the external factory case of the UVC extends up to hide it, or it’s a bubble top where the hot pipe is extended down from the top to allow a pocket of air to be trapped to use as expansion. 

If the bubble top has depleted, you simply drain the UVC and refill  to replenish the bubble or it’s the other type and the dead EV needs to be replaced immediately. 
If you leave the ruptured factory EV in service you’ll eventually have a full and catastrophic failure and a flooded house to boot. The internal steel body of the EV ( if it’s not the bubble top gone ) rusts away day by day, exacerbated by the constant heat and influx of fresh oxygenated water, and perforated. At that stage the cold mains pressure is free to escape and flood your house. For good measure, that usually blows whilst you are out of the house and the cold mains is constant so it keeps pouring out until you arrive home…….

 

It doesn’t sound like your plumber is very experienced in UVC installs / repair I’m afraid. He may be a good general plumber, but this is a terribly dangerous scenario if the factory EV has failed, or a bloody expensive unnecessary repair if it’s just the bubble that needed regenerating.

 

Have a look to see if the lid of the UVC comes off, easily, and you’ll have your answer. 

So mine is the bubble top… Megaflow HE 210. It has instructions on side to replenish bubble. It was already drained to change the TRV. Reading online it seems fairly common for these to break down based on my google searching with folks installing an external EV as a workaround / solution.

 

On mine A white EV has been installed on the cold water inlet to the cyclinder.

 

I will have somebody else check this in due course just for peace of mind.

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For completeness... I've added some pictures of the replacement TRV which I believe is wrong spec... Was originally 10 bar; now 7. I guess arguably this makes the cylinder safer but must be a reason they use a 10 bar. In addition I've taken a photo of the take off for the 18L white expansion vessel which is just below the PRV. Also taken a picture of the replacement PRV which again i'm not convinced is correct specification.

 

 

IMG_5074.jpg

IMG_5075.jpg

IMG_5076.jpg

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The T is before the PRedV is incorrect. The effort they went into chopping pipe and adding the T was a waste of time and money, as the correct position would have been the blanked off / already available 22mm balanced draw off union seen on the “control group” aka multi-block.

I will concede that the retro-fit of the EV is a better / longer term solution, but ONLY if the pre-charge pressure is tested and checked every year during the annual G3 service & inspection. 
 

The 7 bar T&PRedV is fine, as it’s downstream of the 6 bar cold mains relief. In honesty, the sooner that ever opened the better. ;)  

Edited by Nickfromwales
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1 hour ago, Nickfromwales said:

The T is before the PRedV is incorrect. The effort they went into chopping pipe and adding the T was a waste of time and money, as the correct position would have been the blanked off / already available 22mm balanced draw off union seen on the “control group” aka multi-block.

I will concede that the retro-fit of the EV is a better / longer term solution, but ONLY if the pre-charge pressure is tested and checked every year during the annual G3 service & inspection. 
 

The 7 bar T&PRedV is fine, as it’s downstream of the 6 bar cold mains relief. In honesty, the sooner that ever opened the better. ;)  

Thank you for being so so helpful. Just wish you were local to me :) one to be my plumber and second to buy you a few beers!

 

So although they have wasted effort installing the EV on a T piece below the multi block, does that actually matter / affect operation? My instinct says it should not matter besides being a wasted effort. Just FYI if you recall I don’t have a balanced cold.

 

These parts are clearly also not heatre sadia parts and the TRV is lower (although that doesn’t bother me if safer) but does this matter?

 

Finally for expansion vessels make noise in operation? You can hear mine making squeaking / creaking noises when water is heating, it’s amplified somewhat by being in the loft.

 

 

Edited by steveoelliott
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7 hours ago, steveoelliott said:

does that actually matter / affect operation?

There is a VERY strict rule about not having any type of valve / control between the cylinder and the EV. The PRedV does have throughput but it’s only the balanced draw point or body of the control group that fully satisfies that requirement. If you look at a few manufacturers installation instructions you’ll see the recommended connection points / detailed criteria. A quick google would have told / shown your guy this info for free. Bottom line is, it needs to be connected to the blanked off outlet on the control group. It can’t stay where it is. ?
 

7 hours ago, steveoelliott said:

Just FYI if you recall I don’t have a balanced cold

Doesn’t come in to it I’m afraid. UVC’s and G3 need to follow the manufacturers installation instructions strictly, and all you can do is add to that. You cannot move things around to try and beat the problem, as that will lead to further failures / compromises. 
 

Bigger question; have you not yet fitted the secondary PRedV and single check non return as per my earlier replies? 

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1 hour ago, Nickfromwales said:

There is a VERY strict rule about not having any type of valve / control between the cylinder and the EV. The PRedV does have throughput but it’s only the balanced draw point or body of the control group that fully satisfies that requirement. If you look at a few manufacturers installation instructions you’ll see the recommended connection points / detailed criteria. A quick google would have told / shown your guy this info for free. Bottom line is, it needs to be connected to the blanked off outlet on the control group. It can’t stay where it is. ?
 

Doesn’t come in to it I’m afraid. UVC’s and G3 need to follow the manufacturers installation instructions strictly, and all you can do is add to that. You cannot move things around to try and beat the problem, as that will lead to further failures / compromises. 
 

Bigger question; have you not yet fitted the secondary PRedV and single check non return as per my earlier replies? 

 

Thank you for your response… there is no secondary PRV or non return fitted as yet. I could not convince the guy to, hence I clearly need somebody else to look at this.

 

Regarding EV position, I can’t as a lay person in principle see an issue with this besides best practice but frankly I am no expert. I will see about addressing this.

Edited by steveoelliott
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I have now told the guy not to continue with any other work… I’m going to get somebody else out next week to take a look.

 

Interestingly I’ve also noticed after running the bath taps for sometime upstairs, I get air coming out / spluttering. May or may not be related of course.

 

I will be sure to advise the person that comes out your advice Nick.

 

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1 hour ago, Nickfromwales said:

The secondary PRedV and single check need to be fitted immediately. They’re not optional ! ;) 

 

Understood... I will put this to the person I have come out next week.

 

Without them, short term, what is the likely result?

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  • 2 weeks later...
On 19/06/2021 at 22:15, Nickfromwales said:

Destroying the new EV. 

Hi Nick,

 

So I had another plumber come out that is definitely G3 certified and they were shocked at some of the errors made and explained them to me.

 

As you stated ,where the previous plumber had placed the EV was the wrong side of the control block and with a check valve on the control block, they had effectively put the EV on the cold water side and there it is doing absolutely nothing for the cylinder as water can't flow backwards from the inlet block.

 

This actually now also explains some other weird behavior I noticed like occasionally hearing the water meter ticking periodically with no open outlets (it's next to my office in a store). Upon inspection it even at times runs backwards! What is clearly happening is where the EV is installed on the cold water without a secondary PRV etc. I am effectively buffering the pressure between the supply pressure as it fluctuates and my internal pressure.

 

So... the action plan now is to move the EV to the correct position (it probably isn't even needed) but since I have it now I may as well have it. I will then have another PRV on the cold main close to the supply (secondary PRV) and a check valve on the output from the UVC.

 

This is all a huge learning experience for me and I appreciate your detailed responses and help Nick.

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2 hours ago, steveoelliott said:

Hi Nick,

 

So I had another plumber come out that is definitely G3 certified and they were shocked at some of the errors made and explained them to me.

 

As you stated ,where the previous plumber had placed the EV was the wrong side of the control block and with a check valve on the control block, they had effectively put the EV on the cold water side and there it is doing absolutely nothing for the cylinder as water can't flow backwards from the inlet block.

 

This actually now also explains some other weird behavior I noticed like occasionally hearing the water meter ticking periodically with no open outlets (it's next to my office in a store). Upon inspection it even at times runs backwards! What is clearly happening is where the EV is installed on the cold water without a secondary PRV etc. I am effectively buffering the pressure between the supply pressure as it fluctuates and my internal pressure.

 

So... the action plan now is to move the EV to the correct position (it probably isn't even needed) but since I have it now I may as well have it. I will then have another PRV on the cold main close to the supply (secondary PRV) and a check valve on the output from the UVC.

 

This is all a huge learning experience for me and I appreciate your detailed responses and help Nick.

Excellent news that your new guy is on point :) You're very welcome.

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