Hot Water Smells Sweet and a bit chemically in Unvented system

topgazza · 19 Jul 2020

Just recently our hot water has a definate sweet smell to it. We have an unvented system heated by a boiler. Before I call my plumber out has anyone any ideas ? i've read loads of different ideas from the extreme to the impossible. I suspect some sort of bacterial effect in the unvented cylinder which has been in for 16 years. Not sure what can be done. Some sort of chemical flush maybe ?

Any tips appreciated

dilalio · 20 Jul 2020

I'd check with your neighbours to see if it's just you and also call the water provider as they have chemists.

What unvented do you have? Is it all taps?

topgazza · 20 Jul 2020

Thanks for replying.

It’s an Ariston system. Taps with two shower outlets. No one else seems to have the problem. My daughter who has an acute sense of taste says it has a distinct chemical/metallic taste as well as the sweetness smell.

The water is scaldingly hot as well. Way above usual safety levels for killing bacteria

picasso · 20 Jul 2020

A strange smell/taste can sometimes be caused by the expansion vessel rubber breaking down also have you noticed any pressure rise in boiler system ?

topgazza · 20 Jul 2020

I'll mention it to my, excellent, plumber who is of course certified to work on these. Ariston say on their website that if one anode is less than 10mm then it is possibly dergrading as well and metal getting into the water. They suggest replacing both the top and bottom. They dont mention and taste or smell although it follows that if magnesium is leaking it will smell and taste funny. They are only £25 each so after 16 years worth changing anyway and giving the system a flush

topgazza · 20 Jul 2020

Update. The hot water from the taps is scalding so not concerned about bacteria. However the smell is hard to define but is definately a chemical type smell and taste. It's not chlorine but the only way I can describe it is that sort of pool cleaning sweet chemical smell. Quite strong my daughter says but it does reduce a bit after a few seconds if a large cup is filled. Possibly a gas that is agitated in the water on opening the tap ? It doesn't go completely, far from it, but it does reduce if left alone in the cup. I had a sip and it tastes like it smells. We dont use the electric heating element in the tank just the boiler to heat the water. The smell is there from every hot water tap in the house.

Unfortunately the guy that fitted it installed the cylinder so the anode is basically facing the wall, nine inches away, the anode is around 18 inches in length. So thanks a lot pal. The pipes, five of them, will need to be undone, the tank turned and the anode taken out and the reverse to reinstall it. I know why he did it as the pipe access is easier to install from the front but he could have turned it another 45 degrees and used another few bends. So all the serviceable parts were accessible. But hey ho, that was 16 years ago so I'll have to stump up for whatever is required to sort it out. I'm assuming its the anode of course but somethings contaminating the water. Mind you my current, great, plumber has never had to replace an anode even on an older system because its degraded so who knows. I've also contacted Ariston to see if they have come across it

picasso · 20 Jul 2020

I would want to find out why the water is scalding hot , you sure both of the electric heating elements are off ? I would also check the two port valve isn't stuck open.

topgazza · 20 Jul 2020

Its the temperature setting to be fair on the cylinder

ianmcd · 21 Jul 2020

topgazza said:
Unfortunately the guy that fitted it installed the cylinder so the anode is basically facing the wall, nine inches away, the anode is around 18 inches in length.

not as big a problem as you think Ariston make anodes that are like a length of link sausages to over come this problem, the older vertical anodes were the full height of the cylinder so you would hardly ever have enough height to replace one so they brought these out, as a side note though if the anodes have never been checked anually as part of the service you will have a job and a half removing the old ones , the nuts swell and you need big boy weetabix to get them out

dilalio · 21 Jul 2020

If we put all UVs in, with full access to elements for replacement, we'd never get them into the places customers want us to put them in.

topgazza · 21 Jul 2020

The anode, I think there is only one near the top of the cylinder and if there is another I cant see it but I'll take pictures. Its an Ariston Contract Sti 150 Indirect Protech, so 150ltr. I like the idea of a "flexible" link of sausages. Its never been taken out so I'm anticipating a difficult job if it has to come out anyway. I agree ditalio. Looking at the cylinder it would have been tricky to position and give full access to everything. It could have been done but maybe I was a bit harsh on the original plumber. The smell is quite strong when the hot water comes out and pouring it into a large mug its very strong but does reduce a bit after a few seconds as I say. I have turned the thermostat down a fair bit but of course the smell is still there of course. It really is a puzzle

topgazza · 21 Jul 2020

I've even tried boiling fresh cold water and seeing if that develops a smell. If its a chemical they put in the water, chlorine etc, or a gas maybe that would also smell when heated but no, it was fine. I will check next door as well

reds42 · 21 Jul 2020

Is it possible for central heating water/inhibitor be contaminating the tank if somehow there is a leak in the heating coil within the tank?

topgazza · 21 Jul 2020

Good point reds. I suspect my plumber will recognise the smell

ianmcd · 21 Jul 2020

topgazza said:
Good point reds. I suspect my plumber will recognise the smell

Highly unlikely, it is of course possible, but the primary water that is in the Heating systemis at a lot lower pressure than the water in th ecylinder that comes out of your taps, so usually it is the other way around if you get a perforated coil your boiler over pressurises

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Hot Water Smells Sweet and a bit chemically in Unvented system

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