Monitoring pH levels... how ?

[Adrian Brentnall]

That might be a plan. At the moment the alkali is drawn from the container it's supplied in - which is a sturdy blue plastic 'squared-off barrel'. When each one runs dry, a new one is swapped in.

Making a permanent 'tank' that's equipped with built-in level sensors might be a way - but then I'd need to lift the 'refills' to pour them into the main tank (unless I rigged up some kind of pump)

It's all I can do to drag these things along the ground, lifting them to pour would be hard work - if not impossible.

[Adrian Brentnall]

Good to know it's not just me !

'Spose so...

[Adrian Brentnall]

At the moment, the dosing chemical is dispensed from the barrel it's supplied in - which has a smallish (probably 1.5" dia) hole in the top. There's already a float switch, plus a filter, and associated cabling / tubing - I might be able to get another 'inline' float switch down there - but it could all get a bit cramped!

'Somewhere' I've got a capacitive switch, which (allegedly) can be mounted externally and still sense liquid levels inside a tank - maybe that's a possibility... Guess I need to see if it can determine the level on a part-empty tank...

[Adrian Brentnall]

Might work - depends if there's room inside the container for it to flip over... Thanks.

[Adrian Brentnall]

Yes

No thanks! Lab tests show that, apart from the acidity, the water's fine for human consumption.

Yes - I've got one of those - must have a play with it and see how well it works. Might be the simplest solution.

[GB]

Is the container size limited to 15 litres?

How easy is it to check the level of alkali and top up? could you make it a routine to check it every time you go in the shed and top it up whenever it's below say 30%?

[GB]

What's the barrel made out of?

[GB]

So the present 5 or 15 litre container size (which is it?) is the practical limit. Little by little we are prising the information out of you. :)

How about a link to the chemical you use and the type of container it comes in?

[Nightjar]

I used to use a version of this pump on 210 litre drums, which are even more difficult to lift. The pumps are cheap and effective and they don't need power.

They use a syphon action, so will only empty the container until the level matches that of the receiver. So, you would either need to lift the container onto a surface that is higher than the top level of the tank or use the pump to part empty the container, so it is easier to lift.

Of course, if you are building your own tank, you could make it larger and capable of lasting much longer between refills.

Colin Bignell

[Brian Gaff]

May seem silly, but if the wheel is already invented and a light activated, why not extend the wires from the light to a relay and operate some audible warning annoying enough to make it through the subconscious brain cells.. grin. Or if no interference in the internals of the unit allowed, then a cheap photocell device against the light which then triggers something more obvious might work. Brian

[Onetap]

Surely you have the solution to the problem right there. You don't need to fit any float switches, capacitative switches or balances, you just need to adapt what's there to give 2 outputs.

The float switch will be an open/closed pair of contacts, presumably with a plug to connect to the controller.

Find a matching plug & socket and make up your own device in an adaptable box; relay on din rail, cable grommets, power supply (old wall wart thing?).

One set of contacts to connect to the existing controller, another set to your own remote 'change tank' lamp.

I did something similar years ago on a packaged water treatment plant that persistently passed hard water and alarmed. Solved the problem and it never happened again. Manufacturers made notes and amended their design. Bastards.

[John Williamson]

The existing sensor gives a signal to say that the alkali has just run out. What's wanted is an extra warning that it's *about to* run out. This needs an extra sensor of some sort, set to send a signal a week or two before the main one shuts the system down, to allow for ordering a new supply of alkali. The ultimate would be a duplicate system set to start when the main one shut down, with an alarm to tell the user what had happened,but that'd cost way too much, even if there were room to fit it.

[Davey]

Like my old car when the fuel level sender failed. I just filled up every 200 miles, (it was in the USA), it gave me a good buffer, and worked fine until I got rid of the car, several years later.

[Davey]

Tell her to go and check it on a regular basis, then! But seriously, I think checking the weight is the way to go for simplicity, that or a separate float switch.

[Adrian Brentnall]

As I've said to other posters, the indication is kind of 'after the event' - I think what I'm really needing is a 'you are about to run out' indication - which is probably a level detector rather than a pH detector...

[Adrian Brentnall]

There's limited room in the shed - and the jollop itself costs ?55 per 5 litres, so I don;t really want to be buying 'lots' of it..

Not very easy - it's in an opaque container.... At the moment, (when I remember ) I do a highly-scientific 'lift-the-container' test every so often and top up if required...

But some kind of 'kiss' & 'automatic' warning would be good

[Adrian Brentnall]

Some kind of high-density plastic...

[Adrian Brentnall]

Sorry - wasn't trying to be deliberately obtuse. I've just been out to check - the 5 litre thing is totally wrong - it's

25 litres (never did get the hang of metric volumes!)

There's a pic of a typical installation here

- it's the big blue barrel on the left

[Adrian Brentnall]

Hmm - but that again will only satisfy the 'you're out of chemical' situation - not the 'you're about to run out of chemical' thing.

Once there's acid water in the system then it's a pain to get it back to pH7 again....

[Adrian Brentnall]

Absolutely right. I had contemplated a 'hot standby' system - (like on the Calor central heating systems you used to get) so it would auto-switch from one tank to the other - while raising some kind of alarm so that 'tank a' couple be replaced before 'tank b' runs out. Twould need some kind of electrically-operated valve (or two) to switch between the two tanks...