Drain plumbing with 90 degree elbows

[copycon]

I'm interested to know the pro's and con's towards plumbing a drain with a 90 degree elbow?

I'm in the process of plumbing my drains, and I had planned to use 90 degree elbows to reduce the angle needed to reach the sump with the flex PVC drain pipes, but now I am not so sure...

I've read that 90 degree elbows reduce water flow significantly, but I've also read that full syphon (herbie) drains do not suffer as bad which is what I am planning to do, so I am not sure of which way to go.

Any advice would be appreciated.

Thanks!

 

[Mr James]

On the drains and returns, my general rule of thumb is to always oversize the plumbing. I usually increase it by 1/4" or so. I believe this will help with your plumbing.

 

[Palting]

Properly sized, elbows are not a problem. Here are two pics. First one is rated at 700 gph. The second one I've run at 900 gph, though I wouldn't recommend you run at that rate.

 

[mcoomer]

While a 90 degree fitting will impede water flow I don't think it's as big a deal on drain lines. You could use PVC street elbows to get more of a sweeping bend rather than the abrupt angle that regular elbows give. Google PVC street elbow for images and you'll see what I mean about it being a smoother turn.

Mike

 

[lordofthereef]

I wnet with 45 degree elbows. My understanding is that two 45 degree elbows is better than one 90 degree elbow in this case.

 

[ducatimikep]

^^^^^^^^^^^^^^^^^^^^^^^^^
X2
Use a pair of 45' instead of a 90'

 

[reefermad619]

I read that the difference in friction between 2 45s and 1 90 is about 1%. And one of my physics professors even said that 2 45s is more firction than 1 90. I think it's pretty much the same thing, but when using 2 45s now you have more fittings to deal with. If it's a drian, I would use a 90 instead of 2 45s placed next to eachother. Where is the drain? Do the draines exit the bottom or the back of the tank?

 

[lordofthereef]

I read that the difference in friction between 2 45s and 1 90 is about 1%. And one of my physics professors even said that 2 45s is more firction than 1 90. I think it's pretty much the same thing, but when using 2 45s now you have more fittings to deal with. If it's a drian, I would use a 90 instead of 2 45s placed next to eachother. Where is the drain? Do the draines exit the bottom or the back of the tank?

I am not sure it is 100% a matter of friction. I think the issue is the air that is coming down the tube along with the water. Again, I am only going with what I have read here. Physics was never my strong point

FWIW the 2 45's aren't placed next to one another in my setup. There is about 6 inches in between Not sure if this makes a difference, but thought I'd clarify.

 

[mgoblue]

Palting...

I noticed your plug laying face up on the floor behind your tank. Looks like a potential fire hazard to me.... just a thought.

 

[aquaman05]

You can purchase long sweep elbows for the drain that will help with the flow.
IMO the less you use the better,if you have 4 or 5 then you might want to think about going a different route.
Maybe someone can post that chart with the flow rates for pvc fittings. I beleive i found it on here at one point.

I am not sure it is 100% a matter of friction. I think the issue is the air that is coming down the tube along with the water. Again, I am only going with what I have read here.
Great point lordofthereef

 

[copycon]

I read that the difference in friction between 2 45s and 1 90 is about 1%. And one of my physics professors even said that 2 45s is more firction than 1 90. I think it's pretty much the same thing, but when using 2 45s now you have more fittings to deal with. If it's a drian, I would use a 90 instead of 2 45s placed next to eachother. Where is the drain? Do the draines exit the bottom or the back of the tank?

The drains exit the bottom of the tank. In my case there are 4 drains total in the form of dual megaflow overflows converted to a herbie design and I am trying to reduce the angle of flex needed to reach the sump.

 

[copycon]

You can purchase long sweep elbows for the drain that will help with the flow.
IMO the less you use the better,if you have 4 or 5 then you might want to think about going a different route.
Maybe someone can post that chart with the flow rates for pvc fittings. I beleive i found it on here at one point.

I am not sure it is 100% a matter of friction. I think the issue is the air that is coming down the tube along with the water. Again, I am only going with what I have read here.
Great point lordofthereef

Long sweep elbow? Hmm... I didn't think of that.

Thanks for the suggestion

For anyone interested:

3/4" = http://www.customaquatic.com/estore/control/product/~product=PF-SP406-007S
1" = http://www.customaquatic.com/estore/control/product/~product=PF-SP406-010S

 

[reefermad619]

I am not sure it is 100% a matter of friction. I think the issue is the air that is coming down the tube along with the water. Again, I am only going with what I have read here. Physics was never my strong point

The OP said herbie style drain, so I figured full siphon and 1 emergency standpipe. So there is no air to worry about. If it were me, depending on the angle that's needed to reach the sump, I would use a 45 coming off the bulkhead, then use spaflex to get to the sump and then use another 45 to get into the sump.

 

[dots]

The losses through fittings are commonly known as MINOR FRICTIONAL LOSSES, significant loss is only encountered when the pipe is already undersized.

When calculating the "head" or TOTAL dynamic head you are finding: Loss to gravity, Loss due to the fluid flow through the pipe, and the loss due to fittings. Of the three, the first two usually account to about 85%-95% of the Total Head in my experience calculating all the numbers by hand. That remaining 10-15% are those "minor" losses and even then it takes a lot of fittings to make an effect. (unless we are talking about a valve used incorrectly)

http://www.advancedaquarist.com/issues/jan2003/featurejp.htm

If your worried about one 90 or two 45's inhibiting flow under full siphon, then your plumbing was already undersized to begin with, considering the flows we deal with....this is all "academic" at most.

The "K" factor of a 45 degree compared to a 90 degree is about 55%, not much but is more, so generally two 45's will have more frictional loss combined rather than a single 90 elbow. Of course the actual flow rates depend on the velocity of the fluid and the diameter of the pipe, we are assuming both are equal here.

In the end, your pump selection has a greater impact on overall system effeciency and performance than an issue such as this, academically speaking that is. If one was concerned, then using a more conservative absolute maximum flow rate through the overflows should be used when determining head and flow conditions for pump selection.

http://www.engineeringtoolbox.com/pump-system-curves-d_635.html

By using the known maximum through the drains, one only need to subtract the minor losses and determine their effect on that flow rate.


The animation here is fun to play with:

http://home.earthlink.net/~mmc1919/venturi.html

 

[steelhead77]

The bulkheads that are required for a standard drilled tank with the Aqueon built-in overflows will only accept 1 inch pvc. Use a 90 use 2 45's it doesn't matter, most of all use a little common sense. Don't overthink things and don't make things harder than they need to be.

 

[jt48]

Interesting thread in my search which I did not find here but maybe someone can help. I understand it to be correct me if im wrong that flow rate is reduced by 50 gph for each 90 degree elbow and 50 gph for every vertical lift. Two questions:
1) how does a tee affect flow? Is it also a 50 gph reduction?
2) is there any flow rate reduction per horizantal travel?

 

[tchndie]

I hooked up the herbie system on my tank and didn't use any elbows at all. I used spaw flex from the bulk head right to the sump and I wouldn't do it any other way if I have to do it again! Keep us posted!!

 

[dots]

Interesting thread in my search which I did not find here but maybe someone can help. I understand it to be correct me if im wrong that flow rate is reduced by 50 gph for each 90 degree elbow and 50 gph for every vertical lift. Two questions:
1) how does a tee affect flow? Is it also a 50 gph reduction?
2) is there any flow rate reduction per horizantal travel?

The actual reduction in flow a fitting has on a system is based on the fluid density, velocity of the fluid, and the size of the fitting. There is no "one" value to estimate the losses a fitting has and needs to be calculated for each scenario. Forget you heard those "rules of thumb".

1) The tee will effectively divide the flow in half at the intersection. As well there will be a slight "minor" loss on both of these branches from the water entering, splitting, flowing through, and exiting the fitting. This loss, which is then converted into equivalent losses in feet are then totaled and added to the "feet of head" lost to gravity in vertical rises and the total "feet of head" lost in the minor losses from fittings.

2. Yes. This is due to the walls of the pipe as the fluid "slides" by. Of the three types frictional energy lost in the system, (from a vertical rise, from the water flowing through the pipe, through fittings), this is the second greatest in combined losses generally. It too is based on the same properties I listed above as a fitting as well as the pipe type and "smoothness" of it. In our applications we deal with PVC generally and this "smoothness" factor is already determined and applied.

 

[jt48]

Thanks for the info. I plumbed 90% of the job when I realized I can make modifications in my layout and eliminate 3 90 degree elbows and provide more room in the sump.