Strange plumbing water control temperature question / advice needed.

[locini]

Hi All,

Merry xmas

I have a general plumbing question for a project I'm currently undertaking, hoping somebody can help me with.
Bit of a weird one which is probably well out of the normal domestic related stuff...

In Nov/Dec - I've just installed over 50 tropical fish tanks in a spare room for tropical fish breeding.
I'm looking for a control solution to control the water temperature during weekly tank water changes - To make things much easier for myself.

The tank water temperature varies in each individual tank for each individual species of fish - but generally is anywhere between 24c - 28c and most tanks are sat around the 24c mark so this is the figure I'm batting for nicely controlled water at.

I looked into a thermostatic control valve which I could install under my kitchen sink and thought i had found the perfect one from Screwfix:
https://www.screwfix.com/p/flomasta...mm/684fa#product_additional_details_container
as the specification details page said it controlled from 5c - 85c
On installation though this was however not the case...

The TMV didn't work for my needs as the minimum outlet I could wind it all the way to the hard stop was 30c. (which is no use to me as this is above the max tank water temperature)

As an interim temporary solution (As my plumbing was in bits after the attempted TMV fit ) I have installed 2 x non return valves and 2 x manual ball valves to manually mix the water to the fish room during water changes.
This is rubbish though as obviously the hot and cold inlet temperatures are variable and every time i need to adjust anything I'm scurrying around under the kitchen sink...
Re Legionella i have no concerns here as I have also installed a low point drain to empty the line after use, and the water will only be used once per week for my water change schedule.

We are recording the whole fish room build for youtube so this is a video of the plumbing situation i need help with to make things a bit clearer.

Any suggestions at all would be much appreciated
Also if anyone knows any smart/electronic controllers that could be changed through an app that would be amazing.
Right now though anything would be better than current set up...

Thanks,
Ian

 

[martygturner]

Your issue is one of disparate temperature variables, if we ignore density or mass ( which we should'nt really) in a themotstaically controlled
shower that's not too much of an issue as the a shower temp of say 38 degrees mixes water at say 55 degrees with cold water at 15 degrees... you can see the maths straight away...55-15 = 40 so the ratio of hot and cold only needs a slight tweek to get to 38 which is achieved by adding a drop more cold. As I said we can ignore the mass of water and its specific heat value as we are just moving a few degrees from full bore mixing at a consistent flow rate for both hot and cold. Ie if you have a a consistent flow rate of say 2 bar on both hot and cold the temp you will get 40 degrees.

But you have the issue of cooling not by a few degrees but by 30 degrees, that means the mass of cold water will be huge compared to the hot water, and most standard thermostatic mixers will not have the capacity to supply that much cold water and if they did their performance would be really shonky.. like all those combi boiler showers out there with un-balanced flows..

Or in other words.. you need to supply hot water at a temperature within the mixing range of any blending device to start with.

If its a combi you could just try lowering the flow temp of the water to minimum whilst you fill the tanks... stored water will be an issue as its kept above the bacteria growth temp.

You may have to use a point of use water heater to get a stable output.

 

[locini]

Your issue is one of disparate temperature variables, if we ignore density or mass ( which we should'nt really) in a themotstaically controlled
shower that's not too much of an issue as the a shower temp of say 38 degrees mixes water at say 55 degrees with cold water at 15 degrees... you can see the maths straight away...55-15 = 40 so the ratio of hot and cold only needs a slight tweek to get to 38 which is achieved by adding a drop more cold. As I said we can ignore the mass of water and its specific heat value as we are just moving a few degrees from full bore mixing at a consistent flow rate for both hot and cold. Ie if you have a a consistent flow rate of say 2 bar on both hot and cold the temp you will get 40 degrees.

But you have the issue of cooling not by a few degrees but by 30 degrees, that means the mass of cold water will be huge compared to the hot water, and most standard thermostatic mixers will not have the capacity to supply that much cold water and if they did their performance would be really shonky.. like all those combi boiler showers out there with un-balanced flows..

Or in other words.. you need to supply hot water at a temperature within the mixing range of any blending device to start with.

If its a combi you could just try lowering the flow temp of the water to minimum whilst you fill the tanks... stored water will be an issue as its kept above the bacteria growth temp.

You may have to use a point of use water heater to get a stable output.

Thanks Marty,

Reply vastly appreciated. Never knew it could be so complicated to get 24c controlled water... Jeezo how we live in blissful ignorance...
I don't have a combi its a stored system so the idea of lowering the flow during the water changes is a no go unfortunately.

Thanks for the suggestion of the point of use water heater - I did think of this solution right off the bat but was trying to avoid as i didn't want to run a water supply into the fish room. (No sink, no drainage) not to mention the electrical side to hook up the point of use. (I will revisit and do more research on this option though)

I'm trying my hardest to not ruin the room and commercialise it with heaters, electrics, wiring, plumbing bla bla as its still my home and one day i will have to move and return it all from a fish room to a normal sun room for normal people ha ha.

Thanks again for your reply