Pump and PVC size

[dburt520]

If I have a pump that is rated at 1500 GPD with a 1.25 outlet and I plumb it with 3/4 inch PVC all the way through, does that mean right off the bat my max flow is reduced by ~ 35-40%?

[slief]

That is a pretty safe assumption. In fact, it will likely be even more than 40%. It all depends on the length of the plumbing, vertical height, fittings, valves and type of material you are using. You will be increasing head pressure and friction loss exponentially by reducing the plumbing size. I always try to go a size larger to reduce friction loss. Especially if there are unions, valves and other fittings.
Here is a head loss calculator that you can use to see what the different size PVC does to your head loss. The pump you choose isn't terribly important if the model you are using isn't included. Just take the calculated head loss from this link and compare that to the flow chart for your pump.
http://www.reefcentral.com/index.php/head-loss-calculator

[dburt520]

Slief,

Thank you for the quick reply. I used that prior to posting and I don't feel it is accurate for my sitation... It calculated my head loss at 27 ft, however my pump is only rated for 12 FT (DC pump). It is pushing water, and a decent amount but I am thinking I want more. Contemplating whether to replumb or buy a bigger pump.

Here is a pic of my plumbing:

http://i1171.photobucket.com/albums/r548/yz400fer69/Mobile%20Uploads/20160325_191226_zpssi78mhxw.jpg (http://s1171.photobucket.com/user/yz400fer69/media/Mobile%20Uploads/20160325_191226_zpssi78mhxw.jpg.html)

[Pilotman520]

There may be some loss from the smaller pipe but not as much as you think. The velocity of the water increases and the flow remains the same. If you are pushing 27ft on a pump that's only rated for 12 it probably won't last very long.

[Pilotman520]

BTW how did you calculate 27ft of head loss? Doesn't look like more than 4 or 5 feet to me.

[ca1ore]

If I have a pump that is rated at 1500 GPD with a 1.25 outlet and I plumb it with 3/4 inch PVC all the way through, does that mean right off the bat my max flow is reduced by ~ 35-40%?

Depends on the pump. One rated for flow will lose more than will one rated for pressure. DC is the former.

GPD = Gallons per Day?

[dburt520]

Well, here is what I did on the calculator:

(5) 90's, (4) 45's, (2) ball valves, (1) Tee, 4 feet vertical, 6 feet horizontal.

It is an RODC 5500, rated at 1500 GPH.

[Pilotman520]

I estimated mine on that just now. I also came up with about 22 feet. I have a 1500gph pump using 3/4 return pipe. I have enough flow thru my sump and I'm not burning pumps up.

[slief]

Slief,

Thank you for the quick reply. I used that prior to posting and I don't feel it is accurate for my sitation... It calculated my head loss at 27 ft, however my pump is only rated for 12 FT (DC pump). It is pushing water, and a decent amount but I am thinking I want more. Contemplating whether to replumb or buy a bigger pump.

Here is a pic of my plumbing:

http://i1171.photobucket.com/albums/r548/yz400fer69/Mobile%20Uploads/20160325_191226_zpssi78mhxw.jpg (http://s1171.photobucket.com/user/yz400fer69/media/Mobile%20Uploads/20160325_191226_zpssi78mhxw.jpg.html)

The head loss calculation is relative to the pump you chose in the calculator so it's not exactly a good calculation but you can increase the plumbing size in the calculator and see how the head level drops. In order for the head loss calculator to be more accurate, you would need to choose a pump of similar flow and head pressure capability.

You plumbing looks very nice and I'd hate to make this suggestion but I would redo the return side. You would be very surprised how much that will increase your flow. 3/4" plumbing will only support so much flow and the fittings reduce it further. Going to a larger pump will likely not result in as much of an increase as you would like unless the pump is pressure rated where as increasing the return pump diameter size will have a substantial impact on flow. What I would probably do is come out of the pump with the 1.25" fitting, increase it to 1.5" and bring that up as high as possible. From there, use a 1.5" T fitting and connect that to each of your 3/4" returns. That should result in a fairly good improvement.

[dburt520]

Actually, the return is what I am refering to. I have 3 1 inch drains, 1 full siphon, 1 with the valve and 1 emergency. The valve is 75%'ish closed to allow the full siphon to work and a tiny trickle down the emergency.

[Bent]

Yeah I hate to suggest cutting that as well, since its really pretty.

My suggestion would be to severely upsize it. I mean like 1.5X the pump outlet.

So if you are an inch and a quarter pump outlet size, then I would get an adapter and run 2" minimum, ditch the 90s and run 45s.

[dburt520]

So if I drilled the tank for 3/4 bulk heads, should I just reduce it right at the bulkhead?

[Bent]

So if I drilled the tank for 3/4 bulk heads, should I just reduce it right at the bulkhead?

Yeah you could. A small amount of restriction at the end is better than the entire run.

But...if you could redrill for 1" or even 2", you could increase the flow even further.

[slief]

Yeah you could. A small amount of restriction at the end is better than the entire run.

But...if you could redrill for 1" or even 2", you could increase the flow even further.

+1

The more of the larger pipe you have, the less friction loss and the more flow you will have in the end. Especially if you have a 90* fitting going into the tank. If you ran the 1.5" or better yet 2" pipe all the way up to the fitting and use a 2" elbow and reduce that down to 3/4", that would be the best case scenario that would provide the most pressure to the 3/4" outlet. The larger you go to the fitting, the less friction loss you will have.

[ca1ore]

Here is a head loss calculator that you can use to see what the different size PVC does to your head loss. The pump you choose isn't terribly important if the model you are using isn't included. Just take the calculated head loss from this link and compare that to the flow chart for your pump.
http://www.reefcentral.com/index.php/head-loss-calculator

It's late and maybe I'm just dense, but why does changing the pump (but nothing else) affect the head loss number?

[Gorgok]

I think the calculator is trying to estimate flow velocity and uses that to then calculate the friction, which will change head loss. That and the outlet diameter of the pump should be the only things that change head loss.

[dburt520]

I just wanted to follow up on this and say thanks for the help/advice.

With 3/4 inch plumbing I was unable to utilize a full 1" siphon - it was to much drain for the return flow. The ghost overflow box would never fill, even with the valve completely closed and 1 of the other drains plugged (I ended up plugging the 2 drains with no valve and the only pipe that was draining water was the one with the valve on it - which was about 50% closed).

I re plumbed my return system this weekend with 1 1/4 pipe all the way through (until the return bulkheads which are 3/4 - split with a loc line Y and 2 round nozzles on each). I can now use one drain as a full siphon, and keep the drain with the gate valve about 25% closed to control the water height in the box and the flow through the pipes (much quieter and exactly as my previous 2 tanks have worked).

I changed nothing else besides going from 3/4 to 1/1/4 pipe and I would say the flow at least doubled.

Thanks
Dave