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Plumbing question: slip unions

DurTBear

DurTBear

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I think the answer is that it doesn't matter but is there any problem/drawback to having slip unions plumbed underwater? I'm plumbing my return line from my frag tank to my main tank and I want to have a slip union for easy disconnect and pump maintenance close to my return pump. It's an Eheim 1250 so it's going to be in-tank. Therefore, the slip union will naturally be submerged. Is it better to keep them out of the tank and dry? Thanks in advance!
 
Durwin, did you ever find out how you're going to attach your eheim to 1/2" pvc? I am using 3/4" flexible pvc hose rather than 1/2" PVC, but I will be using poly vinyl tubing, and a thread hose barb and a hose clamp.
 
Cool, thanks Phong.

Ant...I found a female 3/8" adapter from Ryan Herko Flow Solutions that should solve my problem. I wish I had just gotten an Eheim 1260 because the problem would be solved because everything would be standard (I think). But 3/8" isn't standard PVC size (it's metric) so it has been quite a hassle to solve. Anyway, I'm using a 3/8" nipple and the adapter goes from 3/8" to 1/2"...going to hard plumb everything. Worked on it for a bit tonight but ran out of fittings which means I need to go back to the hardware store yet again...haha! Just added a pic of the adapter in my build thread if you want to check it out.
 
I agree with Phong, the unions are all PVC to begin with, I have 2 unions running from my return pumps submerged in the sump.

To answer Ant's question. If your pipes are standard, it is relatively easy to reduce or increase the size of pipes coming out of your pumps with PVC. If the pumps output is MPT, then you would find a 1/2" FPT on one end and either a slip or threaded on the otherside and from there go from a 1/2" to 1" for example. Hope that made sense. Home Depot is a good place for standard parts. You can always check out marinedepot's site just to see all the options.
 
Where did you find 1/2 inch pvc? I am putting together a 65 and was at Lowes this past weekend. The smallest OD I found was 3/4 inch.

Thanks!
 
[quote author=DurTBear link=topic=5476.msg68119#msg68119 date=1228883005]
Ant...I found a female 3/8" adapter from Ryan Herko Flow Solutions that should solve my problem. I wish I had just gotten an Eheim 1260 because the problem would be solved because everything would be standard (I think). But 3/8" isn't standard PVC size (it's metric) so it has been quite a hassle to solve.
[/quote]

www.mcmaster.com :p

310 Maximum Pressure (psi)
4' Transparent 49035K22 $5.20
8' Transparent 49035K82 $8.38

620 Maximum Pressure (psi)
5' Dark Gray 48925K22 $5.54
10' Dark Gray 48925K42 $8.52
 
[quote author=georgec link=topic=5476.msg68228#msg68228 date=1228927087]
Where did you find 1/2 inch pvc? I am putting together a 65 and was at Lowes this past weekend. The smallest OD I found was 3/4 inch.

Thanks!

[/quote]
Lowes, HD, OSH are carry them. Sometimes they just run out.
 
[quote author=DurTBear link=topic=5476.msg68253#msg68253 date=1228931051]
Gomer, do you think it would be best to just use 3/8" pipe all the way through the return line?
[/quote]

yes. larger will create more head and smaller restricts the flow :)

HTH
 
George...Lowes has the BEST 1/2" PVC available...SCH200(IPS)! This is thinner walled and has almost the same interior volume of 3/4" SCH80. Get this and you'll be very happy.
 
[quote author=GreshamH link=topic=5476.msg68416#msg68416 date=1228953828]
[quote author=DurTBear link=topic=5476.msg68253#msg68253 date=1228931051]
Gomer, do you think it would be best to just use 3/8" pipe all the way through the return line?

yes. larger will create more head and smaller restricts the flow :)[/quote]HTH
[/quote]


I was always under the impression that head is head.. Whether the pipe is 10" in dia or 3" in dia for every foot of vertical rise you will get .433psi of head pressure.. The volumes will be different but the head pressure will be the same.. I do a ton of business with Ryan Herco weekly. If they don't have what you need you might want to check with Harrington Plastics as well. They have a couple of offices.. I think one is in burlingame.. They have both npt/ips sizes as well as metric.. If you have anything else like bspp or something you might have to source it through mcmaster carr...

Georgec hd and osh usually will have pvc in sizes ranging from 1/2"od which is 3/8" nominal and up.. regular 1/2" pvc is in actuality closer to 3/4" od.. The pipe sizes are normally given for the ID of sch 40.. If you are using sch80 or 120 then it changes.. If you use sch 10 you get more volume but thinner walls... I use the sch 10 stuff for all my return lines due to its greater volume and cross section.. As long as its properly supported over the horizontal run you will be fine..

and yes the unions are perfectly fine to put underwater.. Most of the tiem I will put the union out of the water then use a hose barb fitting off the union.. that way I don't have to worry about any vibrations caused by the return pump or stress caused to the piping or my return bulkheads caused by improper alignment of the return pump to the pvc
 
[quote author=fishnfst link=topic=5476.msg68423#msg68423 date=1228954443]
[quote author=GreshamH link=topic=5476.msg68416#msg68416 date=1228953828]
[quote author=DurTBear link=topic=5476.msg68253#msg68253 date=1228931051]
Gomer, do you think it would be best to just use 3/8" pipe all the way through the return line?

yes. larger will create more head and smaller restricts the flow :)[/quote]HTH
[/quote]


I was always under the impression that head is head.. Whether the pipe is 10" in dia or 3" in dia for every foot of vertical rise you will get .433psi of head pressure.. The volumes will be different but the head pressure will be the same.. I do a ton of business with Ryan Herco weekly. If they don't have what you need you might want to check with Harrington Plastics as well. They have a couple of offices.. I think one is in burlingame.. They have both npt/ips sizes as well as metric.. If you have anything else like bspp or something you might have to source it through mcmaster carr...

Georgec hd and osh usually will have pvc in sizes ranging from 1/2"od which is 3/8" nominal and up.. regular 1/2" pvc is in actuality closer to 3/4" od.. The pipe sizes are normally given for the ID of sch 40.. If you are using sch80 or 120 then it changes.. If you use sch 10 you get more volume but thinner walls...

[/quote]

Think of it this way. The amount of water contained in a 10" is far greater then a 3". 10" is much more friction due to more available surface. Gravity doesn't change, but the shear fact you have more volume creates a situation where the pump has to move more. FWIW this is what a few Aquatic engineers have told me, but in experience I can see what they are saying. :)
 
That is true Gresh.. flow wise it will create more resistance but head pressure still remains constant.. like putting a bunch of 90's in will restrict flow but the head will not .. change.. You could have a 1000g tank that is 10 feet high and if you put a gauge at the bottom of the tank to see what head pressure you have it will read approx 4.33psi.. A 5 gallon reservoir that is 10 feet high will read the same head pressure..

I get confused sometimes with cross terminology and the context it is used in...
 
Being I have no "official" training I tend to use words rather loosely :)
 
I seem to recall from my simply flow patterns I would study is that larger is better because while yes there is more surface area for the water to "Grab" onto, the over all volume of water that is slowed down as a percentage of total volume is much lower. I seem to recall writing a program to show the physics of what is happening (keeping things simple by removing rotations), which told the story of what I just said.

That being said, when you enter the dynamics of mechanical pumps that physically move the water all bets might be off, something I realized when I used a spiral twisty hose (ends lopped off) as my top off hose to drag to each tank... figured hey water came out of it no problem when attached to the water faucet, should be no problem if I hook a pump to it... whoops, forgot about the fact the faucet puts a steady 40psi out that doesn't change, pumps on the other hand...
 
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