Water tank monitor

Besides the clear tube does anyone have a good water level monitor for the Oka stainless steel water tank?

Peter, most caravan dealers stock water tank level monitors and most work on the principle that water conducts electricity. (A few use ultrasonic level detection).

A probe (sender unit) is inserted in the tank and connected to a display unit which monitors several sensors on the probe to determine the water level.

You might want to check out this local manufacturer, RV Electronics .

Sender and display .

I haven't used this make myself but I've made my own using the same principle and it's quite easy if you are into electronics, and I'm happy to share my info. Silicon Chip magazine published a DIY project on the subject a few years ago and mine's a modified version thereof (flashing dashboard light when the level gets low). It's extremely handy and much easy to use than reading that grubby little piece of plastic tube where you can't see the level anyway.



Note that most display modules don't include the sender unit which needs to be bought separately. The sender unit needs a hole drilling in the side of the tank and fixes from the outside via a sealing grommet. (Avoid those which have several small sender "bolts" which each need to be screwed into the tank. They risk leaking and are not suitable for a conductive metal tank anyway)

Peter
I have these meters from RV Electronics in my van and they are not very accurate. They register the tanks as full for a long time, drift to half full and then show empty a few litres later. Not satisfactory if you are trying to monitor your water supply.
These is another left field solution which basically works the reverse of your household water meter.

These Savant water meters are actually a counting flow meter that you plumb into your water line. You program the meter with the capacity of your tank and it counts backwards towards zero, the count value being the litres remaining in your tank.
They are difficult to obtain in Australia but here is a link to a UK site with a large range. A google around might find other suppliers.

And a number of Ebay suppliers

Just be careful if you order because you need a count down meter, not a flow meter.

They look like a good idea, I've just asked my Chinese contact if they can supply them or advise me of a supplier as well as cost.

Peter and Sandra James OKA 374 wrote: They look like a good idea, I've just asked my Chinese contact if they can supply them or advise me of a supplier as well as cost.

Peter
Our caravan club is in direct contact with the manufacturer in Taiwan. I have 4 on order but I can't remember the cost.
We are looking at importing a fair number of them, but in a 12v version without the battery setup they have now.

Reason being that the motion of the caravan clauses the impeller to work and give an error in the countdown. With a 12v one we can switch the meter on and off with the pump without resorting to relays, resistors etc for the meter power. The meter retains it's memory when off and doesn't register the back and forth flow.

PeteFox wrote: I have these meters from RV Electronics in my van and they are not very accurate. They register the tanks as full for a long time, drift to half full and then show empty a few litres later.

Pete, there's no theoretical reason for that, mine uses the same principle and is very accurate (twice the number of sensor levels) and reliable. Must be a design/manufacturing issue.

They will show full for a while if the sender is not fitted right at the top of the tank so the first sensor is some way down, and if the electronics voltage is not supplied from a well regulated source, the readings can vary as the 12v battery voltage goes up and down.

There's nothing wrong with flow meters, most car trip meters use one, but they can only provide an accurate tank level reading if the tank is first known to be full, and there have been no leaks.

In my case, I'm not so much interested in how much water we've used as how much is actually in the tank. We have had an occasional leak and on an outback trek this is important go know.

Just my alternative take.

dandjcr wrote:

PeteFox wrote: I have these meters from RV Electronics in my van and they are not very accurate. They register the tanks as full for a long time, drift to half full and then show empty a few litres later.

There's nothing wrong with flow meters, most car trip meters use one, but they can only provide a accurate tank level if the tank is first known to be full, and there have been no leaks.

In my case, I'm not so much interested in how much water we've used as how much is actually in the tank. We have had an occasional leak and on an outback trek this is important go know.

Just my alternative take.

Dave
The implementation in the Kimberley Karavan must be fairly poor then as all the owners have the same issue.

These meters we are buying are a countdown meter, so you program in your tank capacity (only needed once) and with each reset of the meter it goes to the full value and counts down to zero from there, so it gives litres remaining.

Just checked, cost for a bulk buy is approx $40 ea.
Pete

No problems Pete, I just have a different view on the subject.

I can't comment on the Kimberley Karavan issue, maybe it is a product design problem.

On a related topic, I also have a 100 litre flexible reserve tank (fits in an irregular space over the wheel arch under our seat base) which is much more difficult to measure the remaining capacity of.

Currently I use some rods laid across the tank connected to microswitches which open and close as the tank expands and contracts. That's worked fine for several years but the readings are very coarse (the left side of my display panel) so I have considered moving to a flow meter or pressure sensor technique for that one.

David

topic also covered here

I would be interested in 2 or 3 of the count down meters.
Cheers
Ewart

They've quoted me $15 each for the standard model if we buy more than 20, otherwise they are $23 each plus postage for both prices.
Shipping might even be free, I've also asked about a 12 volt version.

This is for the Savant Digiflow ?

At a working current of 1mA (1/1,000 A) or 0.015mA (15/1,000,000 A) at rest I don't think a 12 volt version really matters. The AA batterys will last for years, especially if lithium batterys are used. A steal at $20

Deano

yes it is the Savant 8100T flowmeter with 1/4" NPT fittings

Dean and Kaye Howells wrote: This is for the Savant Digiflow ?

At a working current of 1mA (1/1,000 A) or 0.015mA (15/1,000,000 A) at rest I don't think a 12 volt version really matters. The AA batterys will last for years, especially if lithium batterys are used. A steal at $20

Deano

Dean
It's not the voltage that matters so much, it is being able to switch the unit off when travelling, and 12v is an easy way to do it.
If left on when travelling the back and forward motion of water in the pipe causes the unit to count, effectively making it inaccurate.

If the unit is switched on and off by the pump operation with a delay (see below), 12v is the easy way to do it, otherwise you need to splice the battery circuit into a relay, or some sort of step down voltage reducer. A resistor is difficult to implement because of varying current draw due to a capacitor being charged somewhere internally.
Either way if the point is accuracy then the meter needs to be disabled during travel and it also needs approx 10 seconds of power after it stops counting otherwise it doesn't save the last countdown value but reverts to the ' tank full ' value.

Pete if you put it in after the pump the water won't move because it's held under pressure or am I missing something?

Rob
Just going on reports from owners of the ten or so already fitted. The club wanted to make sure before we order a heap.
Although there is no flow, it's still a liquid so there must be movement in there somewhere. The unit registers the impeller movement and I don't think it matters which direction it moves, backward bad forwards might do the trick.

From the website

". Had a call from ... who is currently in transit, to tell of a problem with figures accumulating after driving down road.
It appears to develop additional litreage while in motion . Figure can be reset to last known at every stop but that is making life a bit too difficult. Questions are being asked before any meters are bought.
O.K. when stationary.
May have to switch off for travel ----Not so bad with a 12v system? "

Also with retaining memory when switched off, it seems to retain the memory if the unit remains powered until the display switches off which is about 10 seconds

That was my thought too, as we feed from three different tanks it would have to go after the pump and as it maintains pressure for weeks when switched off I wouldn't have thought there would be any water movement in the system. Maybe because it is the towed KK it moves around a lot more than a vehicle.
The other problem I can see is that as all our plumbing is under the floor it will have to go underneath as well plus you would have to go outside to read the display.

Peter and Sandra James OKA 374 wrote: That was my thought too, as we feed from three different tanks it would have to go after the pump and as it maintains pressure for weeks when switched off I wouldn't have thought there would be any water movement in the system. Maybe because it is the towed KK it moves around a lot more than a vehicle.
.

Not in a KK. KKs have crap taps. In mine, one pump takes a few seconds to re-prime after every trip.

The only time the pump ever runs between "uses" in the Oka is when the hot water cools, I'm guessing the water "shrinks" enough to drop the pressure so the pump starts up for only a couple of seconds usually in the very early morning.

Would a non return valve help?
What is the difference between NPT and BSP ?
I would use one on the drinking water tap and one for the other taps, would they restrict the flow to the shower if the meter was to small?