Polluted drinking water from Dishwasher

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my plumber was here just this morning and left me a message to say that he fitted a double check valve. what difference would it make?
 
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Regsmyth - by disconnecting I just mean turning the blue lever.

I know, it's a real thinker! I'm going crazy because we have a brand new dishwasher that we can't use unless we compromise having drinking water!
 
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If turning the valve off stops the taste, yes, get a new hose. They are usually blue. You can get an extra-long one which makes it easier to move the machine. There are some white ones made for drinking water that are used for water softeners. Don't lose the rubber washers in the connectors. You may need water pump pliers for the plastic nuts. The hose in your picture doesn't look new to me.



BTW the flexible waste hose is not fitted correctly, it should be looped up with the top of the loop higher than the water level in the sink. The way it is done now will make the machine smell, but it won't get into the drinking water.
 
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Hi Andy,

To clarify, is the water inlet the dark grey pipe in the first photo? I'm assuming inlet means that the water goes in to the machine from this pipe as opposed to out.

You think the taste is residue from inside the pipe? Is that correct?

If yes to both, does that mean that the drinking water that comes out of our tap is via the dishwasher?
 
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I've just found this on a website...

• You should isolate the hose using the valve that turns off the cold water to the appliance. If the cold tap water is then satisfactory you have found the cause. The solution is to fit a non-return valve so that water standing in the hoses does not get drawn back into your drinking water when you operate the tap.

I should also mention that the plumber fitted a non return valve to no avail
 
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my plumber was here just this morning and left me a message to say that he fitted a double check valve. what difference would it make?

As already said, that doesn't look like a double check valve, it doesn't look long enough, a double check valve is basically two singles in series, and there should be a characteristic screw in the middle to allow checking the first half of the valve is working correctly:

http://www.aqua-check.co.uk/index.php/15mm-double-check-valve.html

As an example, double check valves are supposed to be fitted to the feed to a garden tap to ensure it's impossible to syphon weedkiller, etc back into the drinking water supply - a single check valve isn't sufficient as a small amount of contaminated water could push past the first valve before it's pushed shut.
 
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Hi,

I'll have to check if there's a screw on the valve when i get home. However, I do trust my plumber. He said he fitted a double check valve so I have no reason not to believe him.

He's fairly insistant that it's a fault with the dishwasher although as I've previously mentioned, I've already paid an engineer from Beko to tell me that it's not! Also, isn't the sole purpose of a double check valve to ensure no bad water can get through? Which makes me think that the route of the problem has to start in the valve of after it. Ie between the valve and the tap??
 
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Ask the plumber if he used jointing compound. If so, have a sniff of his tub of it, or wipe the tiniest trace inside a glass, add water, dip your finger in, have a taste. If it is jointing compound, or flux from a soldered joint, it will wash away in time. It is not poisonous and used to be perfectly normal.

You can usually smell compound rather than taste it. Soldering flux is rather sour. In either case it will wash away in time, and if you run the tap for a couple of seconds before drinking it, the traces should go.

I still think the grey hose looks old and dirty (are those spots of paint on it?)

It is possible to use PTFE tape on olives instead of jointing compound (this is the same material as is used to line non-stick pans and perfectly wholesome) but some plumbers are very old-fashioned and dislike it.
 
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The plumber did solder the pipework. If the soldering flux goes away with time then this is not the problem. We had the kitchen fitted and dishwasher installed 2 months ago. The taste would have gone by now. We are only getting around to addressing this now as we've been busy with other projects. We currently drink the bath water (filtered) and continue to use the tap water only for washing up and boiling. Not a great situation!

I have questioned the plumber re the double check valve. As pointed out by 'AL66' it does look as though the valve he's fitted is single. He's not yet replied.

I know that one of the hoses came with the dishwasher. The other is new from Screwfix. The spots you see are paint.
 
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Might be worth having a word with your water supplier. It could be a coincidence that the mains water has become contaminated at the same time that your dishwasher was fitted.

Any residual flux in the pipework would be washed away in a very short time and although I have known some flexible cold water pipes breakdown producing small pieces of relatively inert rubber flakes I have never known them to create a 'taste' when fitted after the point where drinking water is tapped.
 
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Hi - it can't be the mains water. When we disconnect the dishwasher (ie turn the blue lever), the water is fine.
 
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Does it still taste same after you run tap water for a few minutes?

I would replace the dishwasher hose.

Daniel.
 
L

longdogs

Some hoses are made from cheap sub standard rubber which is why they can add a taste to the water supply. The same goes for flexible tap connectors.
 
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But it still begs the question Irrespective of what the hose is made of, or contains, there is no way that hose contaminated water should be able to get back into the upstream domestic supply line - unless the domestic supply line itself is severely restricted such that opening the tap causes a massive fall in pressure and the entrained pressure within the hose is managing to seep back through the check valve into the drinking tap.
 

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