I am having trouble finding the answer to this question online. I know that the difference has to do with the thickness of the pipe, but some sources say it will work and some do not say at all. I ask because I want to use a schedule 80 gate valve with schedule 40 pipe and am not sure if it will work.
will schedule 40 pipe work with schedule 80 fitting?
- Thread starter TauReef
- Start date
gottalikesharks
New member
I have some 3/4" sch 80 elbows that fit perfect with 3/4" sch 40 pipe so I would say yes.
The outer diameter measures the same for both SCH 40 and SCH 80 pipe-- fittings have the same inner diameter.
The outer diameter measures the same for both SCH 40 and SCH 80 pipe-- fittings have the same inner diameter.
planedoc
New member
Outside diameter of pipe is same. Internal diameter of schedule 80 is smaller which restricts flow but adds thicker walls that can handle more pressure. So most sch 80 will fit sch 40. It's not a difference of OD its a difference thicker walls and a smaller I'D. Fish tank operate in sch 40 pressures. But if you can only find a valve you want in 80 than you will lose flow. Don't install 80 valve in drain line
Why wouldn't I want to do this? I need a way to restrict the flow to get my herbie drain to work. What would I use instead?
Realposition
New member
I used a sch80 gate valve with sch40 pipe. All my sch80 fittings worked fine with sch40 pipe
kcress
New member
Since the sch80 has a smaller ID you will have a localized restriction. Sometimes localized restrictions catch things and cause a build-up on their abrupt shoulder. Not the end-of-the-world but you'd want to avoid it if you can.
Thanks for the info everyone. I think I am going to try one of the 1'' spears gate valves that BRS sells. From what I am told it will work with the basic 1'' sched 40 pipe that HD sells. As the idea will be to restrict flow slightly to get my full siphon going I am not too concerned. There will be an emergency drain as well as a strainer for the main line just in case it gets clogged. Thanks for the info everyone.
planedoc
New member
Thx Kcress
If your doing a herbie it will work . Bottom line is high quality valves are hard to find in sch 40. You didn't say what you were doing and normally you don't want any part of your drain line to be smaller than initial opening. I'm glad to see you are doing the best drain system there is.
redtop03
moved slow
it's probable not the case in all brands of PVC but with all that I've used,the fittings and valves are all the same in thickness and same ID with schedule 40 and 80,just the color is different....the pipe walls in schedule 80 is much thicker with the reduced ID
so with what I've used,the localized restriction isn't there,what I've used all came from Lowes other brands are probable different,and this is definitely something to make sure doesn't happen,especially with the drain plumbing
rickztahone
New member
With all of this being said, does anyone know where you can buy valves in schedule 40? I have been unsuccessful in finding any. I plan on running a bean animal setup, and the only true union ball valves I have seen seem to be schedule 80, which the bean animal page seems to depict as well.
SGT_York
New member
The good gate valves are sch 80. The cheap ones are 40. In a siphon line it makes zero difference. You restrict the gate valve so your pipe Internal Diameter is almost no difference. The benefit to the sch 80 valves are high, they last and can take a beating.
All US pipes are measured by outside diameter the schedule doesn't matter unless you are fitting the inside.
All US pipes are measured by outside diameter the schedule doesn't matter unless you are fitting the inside.
rickztahone
New member
thank you for the quick answer. Schedule 80 true union ball valve it is 
uncleof6
Active member
[SIZE=-1]PVC Pipe is identified by the ID (Inside Diameter) and is referred to as a "nominal" size which means "in name only." However this confuses people and most novices try to use the OD (Outside Diameter.) PVC pipe and fittings are matched by the nominal size, and there is no need to consider the outside diameter. Schedule, SDR, cl, relate to the pressure rating of the pipe, hence the inner diameter varies. Sch40 is thinner walled than sch80, and therefore has a larger inside diameter. Larger inside diameter is better for our purposes, as there is no concern about pressure. SDR-21 (cl200 at home depot) is even better as the inside diameter is even larger.
Sch80 valves should be preferred for their longevity over sch40. Gate valves should be preferred to ball valves for flow adjustment, and ball valves are better suited to on/off operation.
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Sch80 valves should be preferred for their longevity over sch40. Gate valves should be preferred to ball valves for flow adjustment, and ball valves are better suited to on/off operation.
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rickztahone
New member
thank you both for that information. I was merely trying to go off the bean animal page. I have no other point of reference and that information is invaluable to me. Is there any other things I should adjust for considering that I am trying to match his design to the T.
rickztahone
New member
gotcha, thank you. I plan on using a lot of unions for maintenance.
uncleof6
Active member
Every union is a leak waiting to happen. If the system is built according to Bean's design to a "T," there is no need to disassemble the system for maintenance and the standpipes/drains are accessible from top to bottom via the removable cap on top of the tee, with an extended bottle brush. That is why they are there. The only place you need a union is at the pump to facilitate its removal.
Quality valves, will disassemble in place for cleaning and seal replacement. There is something to be said for buying 1 quality gate valve for the siphon, rather than three ball valves, to have a valve on each drain line.
rickztahone
New member
Yes, per the current post about gate valve over union valves, I have switched my wishlist for this piece. With regards to the unions, I did plan on putting them AFTER the depicted bean animal design so that I can take it apart later if need be.
I have followed your advice so far and it falls in line with what I have been researching so I know your advice is sound. Thank you for taking the time to help a new sumper, but not a new aquarist
