DIY Drinking water level indicator

AntarcticPilot

AntarcticPilot

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Cambridge, UK
www.cooperandyau.co.uk
Capricious is a Moody 31 with a built-in GRP water tank. No problem with the tank; everything works fine (the calorifier is another matter!). However, running out of water tends to cause problems with the water system,so it is desirable not to run out of water!

I've looked at commercial tank indicators which seem to have lots of bells and whistles and cost silly amounts of money for what they do.

Does anyone know of an inexpensive way of getting a simple "nearly empty" indicator? All I really need is a red light saying "Fill the water tank"! There is NO access to the interior of the tank without taking the entire top off, and the filler is not a vertical drop. I've seen a system with strips of metal foil on the outside of the tank; in terms of ease of fitting, that would be excellent.

I don't want to drill additional holes in the tank; something that fits on the exterior of the tank wall or uses the pressure on the tank side of the pump would be ideal.

I can probably manage to assemble a Maplin's electronics kit, but not anything more complex.

Any ideas?
 
In an earlier post on this, someone uses a water meter on the output from the tank. Reset to zero on filling and monitor as it increases to tank capacity. I don't know about costs though.
 
AntarcticPilot said:
. . . . But I really don't want to make new holes in the tank, . . . .
Click to expand...

You don't need to make any extra or new holes in any part of the tank!

The white pipe I mentioned can be fitted anywhere along the pipework to your taps or shower unit. You would need to fit a 'T' piece in this pipe and the white pipe needs to be vertical fitted to any vertical bulkhead. It could also be used for the diesel tank if you need to use it for fuel level.

Water finds its own level so the top of the white pipe needs to be higher than the top of the tank or you can reduce the top of the white pipe down to windscreen washer pipe and take this higher than the water (or fuel) level. Of course, the lower end of the white pipe needs to be at a level near the bottom of your tank.

If you only want a 'low level' warn, you could get away with only one or two LED's. Probable cost something less than a fiver. :D
 
AntarcticPilot said:
Have I got this right?

You insert into the tank a cable that has exposed conductors at intervals along it. This plugs into the indicator box.

So, it requires inserting a cable into the tank. Not impossible, but needs thinking about; because of internal woodwork and so on this might not be easy on Capricious.
Click to expand...

Yes, you are correct, I used a small cable gland fitting to hold the wire, heat shrink to a length of 3.2mm st/st rod, cut to the depth of the tank.
Drilled an 8mm hole for the wire/rod & 3 2.5mm hole to secure the gland, double sided tape for the indicator box.
longest part of the job was preparing the 12 core wire, exposed at the chosen intervals, you could use less wires if you don't want so many increments.
 
lenseman said:
You don't need to make any extra or new holes in any part of the tank!

The white pipe I mentioned can be fitted anywhere along the pipework to your taps or shower unit. You would need to fit a 'T' piece in this pipe and the white pipe needs to be vertical fitted to any vertical bulkhead. It could also be used for the diesel tank if you need to use it for fuel level.

Water finds its own level so the top of the white pipe needs to be higher than the top of the tank or you can reduce the top of the white pipe down to windscreen washer pipe and take this higher than the water (or fuel) level. Of course, the lower end of the white pipe needs to be at a level near the bottom of your tank.

If you only want a 'low level' warn, you could get away with only one or two LED's. Probable cost something less than a fiver. :D
Click to expand...


Thanks for the clarification - that's very clear. It wouldn't work on the pipes to taps etc., as they are all downstream of the pump. But it would work where I need it, using a T-piece on the outlet from the tank. In fact, this idea coupled with the sensor suggested by the other poster would work very well; I'd fit the sensor cable inside a suitable piece of rigid pipe T'ed off from the outlet from the water tank, with (as you suggest) a narrow gauge "breather" pipe going well above tank level.

As always, this forum is a very good place for getting ideas and practical suggestions.
 
AntarcticPilot said:
Have I got this right?

You insert into the tank a cable that has exposed conductors at intervals along it. This plugs into the indicator box. . . . . .
Click to expand...

I think you will find it has an external module which needs to be plumbed in exactly as I have suggested in Message #7 above. :rolleyes:

The e-Bay one is a pukka one with a wizz-bang, nice-looking indicator panel. It is possible that instead of reed relays they use a tube (module) which senses current flow between two wires as they are covered or uncovered with the water inside the tube (mordule). ;)
 
How about using a water level sensor from a washing machine? These use air pressure which increases as water is pushed up the pipe towards the sensor. I think, that if you play with the length of the tube you would have some control as to when the switch activates.
 
Wunja said:
How about using a water level sensor from a washing machine? These use air pressure which increases as water is pushed up the pipe towards the sensor. . . . .
Click to expand...

This is the sme principle as the Reed relays above but you have to obtain a washing machine pressure sensor which could take time or money (much more expensive than a relay, resistor and an LED) and then you still have to play around with pipe length and position.

It would still need to be 'Tee-d' into the outlet pipe from the tank.
 
Paul, fit a "T" in the outlet pipe low down, and attach a sensor from a washing machine or dishwasher to it. (these sensors have a spring and diaphragm which actuate several switches, and trap a column of air whose pressure varies with the height of water in the tank working on the "U" tube principle). That means no extra holes in the tank.
A simple circuit would allow an LED or other device to light when the water reached a preset level. The sensor would be mounted higher than the tank top, and be connected to the "T" by the tube with air in it. I would suggest an extra pushswitch (push to test)in the circuit to avoid bogus alarms when the boat heels or the pump is run. If you REALLY wanted to , you could wire all the switches in the sensor to a series of different coloured LEDs.... now I'm being silly.
 
My DIY skills are fairly limited, and some of the more "basic" suggestions involving reed relays or pressure switches may be beyond me - at least, not with any certainty of them working, and certainly not with any expectation of a neat job!

So far, the best suggestion looks like being the sensor from eBay coupled with a T piece on the water outlet from the tank to provide contact with the water.

Lenseman (any relation to E.E. "Doc" Smith???), if I've read the sensor mechanism for the eBay kit correctly, it works by sensing resistivity changes as conductors are in air or water. I like that one as it is a ready-made solution for the sensor, with a nice clear display of the water level.

As always, many thanks for the suggestions!
 
I fitted the following to my M31 this year - not bad value compared to others and no access to the tank required, just cut the outlet pipe and insert the push-fit sensor and wire up the display. Works well.

http://www.hendersons.co.uk/boattank/page10.html

inline%20sensor.jpg

compact%20water.jpg


Jonathan
 
Thanks

Many thanks for all the suggestions. I have invested in the Kemo M167 sensor (the one on eBay), and will plumb in a suitable tube for it to operate in. This looks like a suitably low-tech solution, with the minimum of alterations to the existing system, and it avoids having to provide a 12V supply to the equipment.

NB, ordering from Boscott's web-site saved me a pound over ordering from the same people via eBay!
 
SPOTTYDOG3 said:
Yes, you are correct, I used a small cable gland fitting to hold the wire, heat shrink to a length of 3.2mm st/st rod, cut to the depth of the tank.
Drilled an 8mm hole for the wire/rod & 3 2.5mm hole to secure the gland, double sided tape for the indicator box.
longest part of the job was preparing the 12 core wire, exposed at the chosen intervals, you could use less wires if you don't want so many increments.
Click to expand...

The equipment (and the price) looks excellent but I'm not too certain about the gland fitting on a holding tank. Can you get the cable plus a wire through the gland to completely eliminate leaks in a holding tank in a seaway, assuming sewage slopping about inside? Also, do the copper conductors last reasonably well in seawater?

Thanks
 
vyv_cox said:
The equipment (and the price) looks excellent but I'm not too certain about the gland fitting on a holding tank. Can you get the cable plus a wire through the gland to completely eliminate leaks in a holding tank in a seaway, assuming sewage slopping about inside? Also, do the copper conductors last reasonably well in seawater?

Thanks
Click to expand...
I have put a large dollop of sikiflex on top just to be sure, but it looked very sealed/secured before. I have fresh waster flush loos, I tinned the exposed wires, so hopefully corrosion will not be a problem.
I fitted early this year, seems fine so far, I will post if otherwise.
 
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