Opinion advice on PVC sump build

[Zallman125]

I'm doing a sump on my 72 gal bow with PVC overflow and piping. I just ordered a rio plus 2500 return pump does 782gph I wanted to know what size PVC would good with this pump. I was thinking either a 1.25 diameter that does 580gph or the 1.5 diameter that does 840 gph. It's about 4 5 ft from tank to sump will I loose anything from the return ??

[mcgyvr]

1" should be fine.. Its only a 3/4" output..
At 4-5ft of head you should get around 450GPH..

[thegrun]

For the drain line 1-1/4" will handle 950 GPH, 1" 600 GPH, so I would upsize to the 1-1/4" for your drain lines. For the return pipe 3/4" will handle 1400 GPH, so there is no need to upsize to 1".

[uncleof6]

A lot of numbers getting tossed about, and none of them are valid...

For you pump outlet line, it should be upsized one size above the actual pump output size. Since the Rio pump is bargain basement, I cannot vouch for how the pump will actually put out compared to the idealized flow curve, however in general, upsizing by one size reduces the friction loss by 1/2 - 2/3 thus reducing the total dynamic head (vertical lift + friction loss) which should improve the pumps output at a given head height. The common practice for centrifugal pumps is the one size increase over the pump outlet size, so 3/4" outlet = 1" return line. You can go larger if you prefer, say 1.25" which will further reduce the friction losses, and the pump output will increase accordingly. However, you will neve get to or past the 0' rating of the pump...3/4" pipe does not have a use in marine systems as the friction losses are excessive in 90% of the cases.

For a gravity feed system, 1" pipe will handle 960gph (16gpm or 6f/s) with minimal losses and noise. For a pump fed system, 1" pipe will handle 2200gph (37gpm or 12f/s) with minimal losses and noise @ 20psi-100psi, (our systems average around 5psi so the losses will be less.) 1.25" the numbers are 1500gph/3750gph respectively.

When discussing drain systems however, everything changes due to the acceleration of gravity...and is based on the bulkhead size, and the type of drain system used. Whereas a 1" bulkhead running full siphon 1" pipe, with a 24" drop will run 1669gph max-theoretical, (1200 - 1300 gph expected,) an open channel (aka Durso) will flow around 50gph, before it drives you crazy regardless of the length of the drop (pipe 1/4 full of water.) and a 1.5" open channel on 1.5" bulkhead will do around 350 gph same conditions and of course the siphon would run ~3750gph. 1.25" pipe/bulkhead will run ~2600gph siphon, and around 200gph, give or take, open channel...

[mcgyvr]

A lot of numbers getting tossed about, and none of them are valid...



except mine :)
1"..check
around 450GPH.. check

[uncleof6]

except mine :)
1"..check
around 450GPH.. check

Where did you get it, and what is the context? It certainly is not valid for a gravity drain open channel, unless you enjoy the sound of toilet flushing, and it is far below a 1" bulkhead/pipe combination siphon (@ 24" drop) 1200gph - 1300gph, and the reasonable limitation for pump fed is 2200gph....

[Zallman125]

well if my return pump is doing about 782 gph id like a overflow around 700-900 if that will be okay? pvc from the main tank to the sump is estimated 4ft of piping if that. not to many elbows either I will have a ball joint on the over flow side and return as well soo still deciding on what size to use 1" or 1.25" or higher?

[uncleof6]

The rio pump is not going to flow what you expect it too. Friction losses will reduce the flow considerably. If you had a pump capable of delivering 700 - 900 gph to the tank after the total dynamic head is calculated out, there are some things you need to understand.

First, if you are running a single drain line, it will for safety's sake, need to be an open channel. A 1" open channel will not handle 700 - 900 gph, in any manner that could be considered reliable or stable. Further, you do not want to put a valve in the line as it will increase the plug risk, and exacerbate the issues with open channels. Even a 1.25" or 1.5" open channel will not handle that flow rate reliably and with any stability. The numbers are a little misleading, as what determines how an open channel will behave is based on the cross-sectional area, and the volume of water in the pipe. The problem starts when the pipe is more than 1/4 full of water.

If you want to hit that flow rate, provided you have a pump capable of it, you will need to run a siphon system. To run a siphon system, you need one siphon line, and one dry emergency at a minimum. 1" pipe would be suitable in this case...

For all practical purposes, if you plan to run above ~ 350gph, you need to run a siphon system, unless you do not mind having problems with the drain system. All the numbers in the world have little meaning, as most claiming their "durso" is flowing xxx gph, are actually unaware of the actual flow rate through the system, because in practical application, pumps do not flow what the rating says...as soon as pipe is attached to the pump outlet, the rating is irrelevant till some math is done to adjust the rating.

[mcgyvr]

Where did you get it, and what is the context? It certainly is not valid for a gravity drain open channel, unless you enjoy the sound of toilet flushing, and it is far below a 1" bulkhead/pipe combination siphon (@ 24" drop) 1200gph - 1300gph, and the reasonable limitation for pump fed is 2200gph....

IMO the OP's question was only about the return piping and there was no mention of "drain" (overflow) pipe sizing.
So my answer is 1" for the size of the pipe for the return plumbing only (sump to dt). 450GPH is the approx. expected flow rate with 4-5ft of head per the pumps datasheet.

[uncleof6]

IMO the OP's question was only about the return piping and there was no mention of "drain" (overflow) pipe sizing.
So my answer is 1" for the size of the pipe for the return plumbing only (sump to dt). 450GPH is the approx. expected flow rate with 4-5ft of head per the pumps datasheet.

Someone brought drain speak into the convo. And even the OP is asking about drains:

well if my return pump is doing about 782 gph id like a overflow around 700-900 if that will be okay? pvc from the main tank to the sump is estimated 4ft of piping if that. not to many elbows either I will have a ball joint on the over flow side and return as well soo still deciding on what size to use 1" or 1.25" or higher?

Be that as it may, the pumps datasheet is highly idealized, and does not account for pipe on the outlet.

The static height of this system as stated by the OP is 4' - 5', I think that could be made more accurate as in exact, but it is what it is. 450gph is not valid, because the total dynamic head on the system will be higher than 4' - 5'. Fortunately (or unforutnately) this is not an opinion. Therefore, 450gph cannot be the expected flow rate. How much lower depends on how well or poorly the return plumbing is put together, and routed. Generally, in most 'hobby' installations this value can easily equate to an additional 2' head height. In very poor installations, it can be such that the pump is driven down to the shut off head height.

How does one come up with a valid number? Well, as pump selection is approached at the hobby level, it literally is not going to happen, (without putting the whole system together and using a flowmeter) as the question is approached from the opposite direction from what it should be. E.G. what job will this pump do, rather than what pump will do this job. The job that needs to be done, is defined as the given head static head height + the friction loss converted to vertical lift and added to the static head height, at a GIVEN flow rate. The flow rate is a constant, not a variable, and the static head is a constant. The friction loss is the variable, and is based on pipe size, the physical length of all the pipe, and number and types of fittings, which influence the velocity, which influences the friction loss. For external pumps, the pipe, fittings, and head height on the pump intake also influence the total dynamic head...These factors can take that 450gph, and reduce it to 100gph or drive the pump down to shut off...this is Basic Centrifugal Pump Installation 101, the size of the pump is irrelevant.

Approaching it in any other manner is just guessing, and the numbers are invalid. The pump should be the last purchase you make, not the first or second...not exactly putting the cart before the horse, rather getting a horse to pull an unknown cart, and no idea how many horses it will take to pull it...

[john08007]

After reading this I think I confirmed what I thought I had to do, dump my durso/return and put in a full siphon return.

I have a 75G cube, 30" tall, I plumbed it up with the included durso setup using a rio 2100 for the return pump. I believe my durso is 1 1/4" or 1 1/2" pipe but it reduces down to go through the bulkhead, below the bulkhead I have 1" pipe going to my sump. It sounds like a toilet is sitting in my living room!

Today after reading some posts it seems like the only way to tune a durso is by the amount flowing through it so I put a valve on my return pump, it had to be cut off about 1/2-3/4 before the water level was stable in the overflow and the flushing stopped.

It sounds like the only answer to my situation would be to use the 3/4" pipe as the full siphon, use the larger one as the emergency drain and run the return line up the back of the tank.

Any other ideas? seems like changing the size of the hole in the top of the durso is useless from what I have read.

[uncleof6]

Best solution, not exactly ideal, but it is the best solution...and yes the solution to a Durso is by lowering the flow rate. Changing the hole size has the exact opposite effect than most expect.

[john08007]

Would it be worth trying to tap the top of my durso and put a small valve at the top so I can fine tune the hole size? I messaged someone else withe the same tank and he's running a Quiet One 4000, that has to put out more GPM's than the rio 2100 I have. He says that he does have a valve on the return line but it is pretty quiet.

[uncleof6]

Would it be worth trying to tap the top of my durso and put a small valve at the top so I can fine tune the hole size? I messaged someone else withe the same tank and he's running a Quiet One 4000, that has to put out more GPM's than the rio 2100 I have. He says that he does have a valve on the return line but it is pretty quiet.

No it does not help the problems associated with exceeding the laminar flow rate for a durso. Although increasing the amount of air in the pipe means that less water can be in the pipe, and decreasing the amount of air in the pipe means more water can be in the pipe, at the expense of stability, and safety if the air is limited too much.

There should always be a valve on the return line, (the output of the pump) as this is the only way to control the flow rate through the system. There should never be a valve on a drain line, unless the drain line is part of a siphon system that incorporates a dry emergency backup. Not sure what you are getting at here, unless it is a semantics problem in calling the drain line a "return line"

[john08007]

sorry about the confusion, he has the valve on the line from the pump to the tank same as I do now. I just feel that this durso should be able to take a lot more flow than it is. I have a rio 2100 with about 6' of head, it's not putting out too much already and I have the valve on it cut off about halfway. Their chart "shows" this puts out 200gph at 6' so I am probably only putting about 50-100gph into the tank.

[uncleof6]

sorry about the confusion, he has the valve on the line from the pump to the tank same as I do now. I just feel that this durso should be able to take a lot more flow than it is. I have a rio 2100 with about 6' of head, it's not putting out too much already and I have the valve on it cut off about halfway. Their chart "shows" this puts out 200gph at 6' so I am probably only putting about 50-100gph into the tank.

The durso is "capable" of handling more flow. The problem is, due to the physics (fluid dynamics) the more flow, the more unstable it will become. Tuning a durso is a balancing act between turbulent flow and "siphon." The less air in the line, the more it will "flow." (A "siphon" has no air in it, hence the high flow capacity.) A durso can be "tuned" very close to siphon, however, it will not exactly be safe, it will not be "silent" and it will not be stable.

Much respect to Richard Durso, for coming up with an elegant solution to the problem he was addressing. Unfortunately, by his own admission, he was not familiar with the physics governing how his invention works. "Siphon" drains were in use at the time, however there was some hesitation in their use as they were/are a flood risk.