Finding out level of opaque tank 3

[looksatstars]

We have a 100' water tower. 1/2" to 3/4" steel painted with lead primer and coating.
We have just installed a transducer in the top that senses the water level to a control panel in the plant. I want to find out how accurate it is (or if it is even close).
Does anyone know how we can tell the level of the water in the tank?
I am think thermal sensing but have no clue about that.
thanks
Dan

 

[GregLamberson]

What about a flow meter on the inlet to the tank?

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[JedClampett]

Do you have an extra port in the side of the tank where you could install a direct pressure gauge? Or a visual gauge that you read with a binoculars?
And by the way, what is a tank doing with lead coating in 2007? Hasn't all that been removed?

 

[stephenw22]

Measure the head pressure at the bottom of the tower (hydrostatic level). You can compare that value to what your level transmitter is telling you.

 

[looksatstars]

Greg...we have a flow meter but no idea where the level is right now.

Jed.. There is no side port. Solid steel. We were told the lead paint is encased so it is not a problem.

sephenw22. there is a pressure guage where the well pump piping enters the Treatment plant but from there it goes thru tideflex valves in the tank so we cant measure the hydrostatic pressure.

 

[GregLamberson]

Strike 3 huh?

Do you have a way of measuring the outflow? If so, as long as you have a flow meter on the inl;et, you could back into that way?????

Greg Lamberson, BS, MBA
Consultant - Upstream Energy
Website:

http://www.oil-gas-consulting.com

 

[rcooper]

Look at it, if there is condensation or dew forming on the outside of the tank up to a certain level, that is where your water is. You could try tapping it and listening for a change in the noise. Rain may evaporate off the side of the tank above the water line faster than below the water line, especially on a hot day. Both of these rely on the fact the water will keep the wall of the tank cooler than the steel above the water line.

You could try tapping it and listening for a change in the noise.

 

[quark]

What is the problem if you have valves in the tank outlet line? Just stop the flow (close any valve downstream the pressure gauge) and deduct/add the height of vertically downward/upward piping and you will have the water column height.

 

[BigInch]

Good one Quark!

http://virtualpipeline.spaces.msn.com

 

[bimr]

Why don't you just take the system water pressure at ground level at off peak hours at a location close to the water tower. That should provide an accurate reading.

 

[cvg]

How about a little more low tech.

in the past I have inspected steel water tanks via inflatable rubber boat entering through the maintenance hatch. Never tried it in 100 feet high tower though...

Or better yet - open the hatch early morning after wells have filled the tank to the top, stick a measuring stick in and check it like a dip stick.

Alternatively, take a 100 feet long piece of string with a rock tied to the end, drop it in, pull it out and mark the string where it is wet.

 

[looksatstars]

rcooper, the condensation is how we checked beforehand. The times I have been out there (afternoon), there didnt seem to be any condensation,plus I would like to drain the tank to see if the transducer is working with the waterlevels. I may have to do the hammer/condensation trick.

quark/biginch/bimr, I assume you guys/gals are talking about a pressure gauge for the water pressure. We have a water tank but we retrofitted it to use a distribution system with pressure tanks and distrubtion pumps so the only access to the water pressure is under the ground.

cvg, good answer but the transducer is mounted to the hatch so if i did your trick the transducer readings may change.

Thanks for the answers, but I may wait till we drain the tank in the fall, and calculate the level from the well meter of the water going in to be sure of an accurate answer.

 

[bimr]

Presumably you have a pressure gauge on your distribution pumps.

If you block the the distribution system off from your pump station, the pumps will then be reading the static water level of the tank.

 

[cr1973]

Flow gage = totally useless
Follow the other recommendations to just measure the static head pressure.

 

[semo]

Unless the line is under concrete you can just use a saddle tap and corp stop to tie into the line. Instead of tapping the actual tank, we have installed a service line from the tank drain to the treatment plant numerous times. The transducer (and pressure gauge) can be mounted on this tap indoors where it won't freeze to give the tank level.

Just be sure to add a valve near the transducer to purge any air that might accumulate in the line. The air bubble will give false readings.

 

[looksatstars]

bimr- there is no pressure gauge at the distribution pumps. The only pressure gauge is at the pressure tanks. I may be able to disengage the pressure tanks then take a reading off the gauge then.
That also reminds me, I can bypass the new Water plant and get a pressure gauge reading off the old well head.
That being said,
The pressure gauge is those cheap needle gauge, will that be able to tell me within a few feet of the height of water in the tank?

cr1973, why do you say the flow meters are useless?
Considering the tank holds 67,000 US gal, I would think a meter that reads X.XXm3 should be fairly accurate.

semo, the transducer that we use is installed at the top and shoots down to the water level.

 

[BigInch]

It should get you at least within 5%... after you hit it with a hammer. Take a reading after each hit then use the average.

http://virtualpipeline.spaces.msn.com

 

[JStephen]

If it's a cheap gauge, you can always replace it with a better one.

If this is an elevated tank, you'll see them sometimes with float-type gauges, more often with pressure gauges. If it's a standpipe, you'll see them with float-type gauges, but not often full-height.

I would try to tap one of the connections or the tank itself and add a pressure gauge. You can get larger, more accurate gauges, and get them calibrated in feet of head rather than pressure.