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Tap Water Temperature

MoFish

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Is it bad to mix hot and cold water so I dont use very cold water when I need to top-up?

Just curious if there is anything I need to be aware of. Been using cold water so far to be safe in terms of water quality from tap.
 
From my research, using hot water in water changes comes with potential/additional risks compared to mains direct cold water. As @MrClockOff says, combi boilers are less risky as they don't store the water like a cylinder hot water storage system - thus, copper leaching due to dwell time becomes less of a problem. Copper is a heavy metal and not great for life at high levels, so a good water conditioner that neutralises heavy metals is key to removing that risk. There is also a slight increase in bacteria due to water stored (in cylinders) needing to be kept at the right temperature.

I have a cylinder-based system and have started to use hot water to prevent long heat-up times. This is the methodology I use for the overtly cautious and paranoid like me. 😀
  • Mainly use cold water, with the hot to 'top off' and bring to an acceptable temperate range.
    • This also addresses dissolved oxygen concerns, as hot water holds less than cold.
  • Have a good de-chlorinator that binds heavy metals to make them safer.
 
From my research, using hot water in water changes comes with potential/additional risks compared to mains direct cold water.
Agreed. The EPA clearly discourage people from using the water from the hot water tap for drinking or cooking as the hot water supply may contain unhealthy sediments such as heavy metals.

Copper is a heavy metal and not great for life at high levels, so a good water conditioner that neutralises heavy metals is key to removing that risk.
A dechlorinator or water conditioner will not remove heavy metals - only an RO system or similar will be able to do that. Some conditioners may temporarily bind the metals making them less toxic for a while until they slowly precipitate back into the water.

Is it bad to mix hot and cold water so I dont use very cold water when I need to top-up?
The "Water temperature math" is fairly straight forward. If your tank is 24 C and you change say 25% with 16 C tap water (fairly typical) the resulting temperature will be 24 x 0.75 + 16 x 0.25 = 22 C - if you do it slowly no harm will be done to your livestock - I do that frequently and not as slowly as I probably should. But in your case, for just topping off, assuming that would be say 5-10% or so... again assuming your tank temp is 24 that would only impose a 0.4 - 0.8 C drop if your tap water is 16 C.

Cheers,
Michael
 
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Agreed. The EPA clearly discourage people from using the water from the hot water tap for drinking or cooking as the hot water supply may contain unhealthy sediments such as heavy metals.
Interesting that that link still refers to lead. Is lead still in common use for plumbing in the US, or are they referring to legacy/old houses lacking updated plumbing?
 
Interesting that that link still refers to lead. Is lead still in common use for plumbing in the US, or are they referring to legacy/old houses lacking updated plumbing?
In some very populous US States lead piping is still quite common in older houses - an estimated 9 million households rely on lead service lines. Its improving, but slowly.

Cheers,
Michael
 
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A dechlorinator or water conditioner will not remove heavy metals - only an RO system or similar will be able to do that. Some conditioners may temporarily bind the metals making them less toxic for a while until they slowly precipitate back into the water.
That is interesting. I found explanations like the one below, but I assume this is not true?
  • Water conditioners chelate (bind) heavy metals, making them biologically inactive and non-toxic to fish.
  • These bound metals remain in the water but in a form that's not harmful to aquatic life.
  • The metals don't "leach back" into a toxic form under normal aquarium conditions.
  • Some plants can (sometimes) break the chelation bonds and use the metals as nutrients.
 
Interesting . Don't think l have ever had an issue , one address had lead water pipes, think the advice was to run the cold water for 5 minutes. The other houses have and present one the blue "plastic" mains ones, l have always added warm tap water to get desired temperature. I think the conditioners l used probably mainly tetra aqua safe, Aquariun from API have always worked. One shop l visted always had water changes on the go and recommended leaving 24 hrs ,bonus of it also then up to room temperature. Maybe in the past some Utility companys had slightly less standards
 
Hi all,
In some very populous US States lead piping is still quite common in older houses
<"Flint water crisis - Wikipedia">
Is lead still in common use for plumbing in the US, or are they referring to legacy/old houses lacking updated plumbing?
It is because they have <"no effective environmental legislation in USA">, meaning that it is more <"cost effective"> to supply water full of faecal coliforms and heavy metals, rather than <"wasting money"> by actually making the water safe to drink.

cheers Darrel
 
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