# Way off topic

#### birdy

##### Newbie
Hmmmm, that didnt work too good.
The graph im refern to is on page 433 in the link.

#### birdy

##### Newbie
Iv seen a few web pages like that one Jeff, but that one just told me that a .5" deep flow at the apex equates to .46 GPM. I dont think so.
Im obviously not do,n it rite.

I need a simple way of measureing flow rate with the V slot method, rangeing from 100 to 10 000 GPH.

They are all talkn big flow rates over wiers.

I just need a graph i can get the boss to print off and laminate so,s a quick look will tell.

Do,n math on the ground wen im covered in mud would be prone to error.

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#### birdy

##### Newbie
Close, but i need it in GPH.
Im only checking water bore flow rates while airlifting, so anythn over 10 000 gph is more than enuf.

#### Mike G

##### Junior Member
Birdy
It's probably not relevant to what you're doing since you're only looking for a very approximate number, but there are two types of gallons;

Imperial (as in British Empire) gallons
and
US (as in ex British colony :usa gallons.

There are 1.2 US gallons in an Imperial gallon (for once theirs isn't bigger than ours:lol

If you think in metric there are 4.5 litres to an Imperial gallon and only 3.8 litres to a US gallon.

Mike G

#### Mike G

##### Junior Member
Birdy
Looking at the calculation methods I'm not sure how accurate they'll be at such low heads of water.
This is what a basic calculation looks like for inches of water head across a 90° V weir.

#### Brian

##### Brian Hebden
Openchanelflow.com has charts for 90degree v

#### groundhog

##### Senior Member
Sorry birdy , are you looking for flow rates in a ditch ? Ive got the equation around here . But uses a coefficient for different materials , such as sod or concrete ?

#### groundhog

##### Senior Member
That was it . Mannings equation. One of the basic truths; flow is most efficient in a channel which will fit in a semi circle.
i suspect you are going to have a constant coefficient, and probably a reasonably constant cross section . two or three points for depth would give you a basic idea of flow vs depth.
adjust with a couple of observations.

#### groundhog

##### Senior Member
Ive never done any water bore work. So im confused isnt it typically constant based on compressor and bore size ? and typically in the 2 gpm range ? as in measure with a big bucket range ?

#### bones

##### Gold Member
http://www.rpc.com.au/pdf/Flow-V-Notch-Weirs.pdf
The bottom graph is the one your after just remember it's in lts per sec, so multiply by 3600 decide then by 4.5 gives you gph.
You want me to come over nd find you some water &#55357;&#56832; After all you seen the photo of what happened when I forgot to turn the last one off.......

#### Mike G

##### Junior Member
Mark (Bones)
Your table gives the same results as my graph, that's reassuring.

I see that you work in Imperial gallons (divide by 4.5).

Be careful if you use the formula in the top right hand corner, the "H" is in metres not mm.

Birdy
You could mark up a pole from Bone's table or my graph, stick it vertically in the water about 60" upstream ( for this graph or table the water height has to be measured upstream at least 4 times the height measured at the V) and read flow directly. That way you don't have to do any calculations at site or even carry my graph or Bone's table with you.

Mike G

#### bones

##### Gold Member
very good point Mike I didn't notice that, most of the drillers just use a V plate, and measure right on the plate, but it is all just an estimate, nothing like sticking a pump down there to see how much comes out.
the last hole here, the driller said 2500 gph at 76 mtrs(251 ft), I can only get the pump to lift 1300, that is the pumps limit, so it shouldn't run out anyway, just put another one down today, and the pump is getting 1700 gph, this one is a lot shallower only 17 mtrs(56ft), this is why more water coming out the top, same size pumps.

#### Mike G

##### Junior Member
Mark
I agree, for the degree of accuracy you and Birdy are looking it's probably insignificant where you measure the height.
I come from the oil and gas industry where we often needed to calculate pump performance very accurately so I tend to be a bit too fussy about details.

Mike

#### birdy

##### Newbie
Thanx Bonsey, thats the bastered i been googlen for, for the last 3 nites.

So, how deep was it in the V on the one you pegged, 15 foot?

Thanx Mike, yes we are only needn a ruf gesstamation of yeild wen we strike water, and its only airlift, so its not accurate anyway.
Youll always pump more out than youll ever blow out.

BTW Bones, iv just drilled me first 200' dry dud.
The first shot got it, only 155', but couldnt beet the clay with the caseing.
F***n missed it altogether with the second shot.
Gota be a very narrow crack in the granet this one.
Ho well, keep punchn holes in the ground, ill get it rite eventualy.