Electrical PVC for Plumbing Drain Pipe

[lund]

I have an unusual application. A sewer pump with a long run (~50 ft with a ~35 ft rise) presently 3" cast iron sections anchored between piers on an outside hillside. The line has a few bends near the (low) pump end. Joints have been deteriorating near the bends and I want to replace the line with something more smooth to fix that and make it a little easier on the pump.

The obvious is to use schedule 80 PVC pipe with long radius bends. BUT when I look at plumbing supply places, schedule 80 PVC does not tend to come with long radius bends. However, I can buy schedule 80 PVC for electrical conduit much more cheaply and I can buy long radius 90 degree and 45 degree bends that would be perfect for what I am doing.

Of course using light schedule 40 pvc for plumbing is not ok for electrical. But I see no reason why I cannot use schedule 80 electrical conduit PVC for this low pressure plumbing drain pipe application. Do you guys see any holes in this? I am pretty sure schedule 80 PVC is schedule 80 PVC and a smooth pipe is a smooth pipe. Interior joints in the electrical version should be just as smooth or better and the material just as strong.

I will also likely wrap the outside portion of the pipe with pipe wrap tape to shield from the sun (probably the main issue for PVC relative to cast iron) and provide a little more vibration damping beyond the pier anchors (every ~4 ft up the hillside). If the expanded **** connectors often incorporated in schedule 80 pvc are an issue, I could cut those off and use standard straight junctions.

Maybe the main issue is dumb inspectors. If inspected, one might see electrical pvc and flip out. BUT a confession. I do a huge amount of work (plumbing, electrical, structural, ...) 98% ignoring inspections since I do all from A-Z. My experience in Cali is that it is too much trouble to go through the process and the dummies often want to call and engineer for anything nonstandard. Then the engineer does nothing other than charge large fees.

What do you guys think. Am I missing something? Know any source of large radius schedule 80 plumbing PVC fittings? I could find none and tight bends would certainly be worse.

Sorry ... put this in tools by accident (no plumbing section). I do not see how to move it (fabrication?). But maybe this is better since this section gets more general people commenting.

 

[nadogail]

I have an unusual application. A sewer pump with a long run (~50 ft with a ~35 ft rise) presently 3" cast iron sections anchored between piers on an outside hillside. The line has a few bends near the (low) pump end. Joints have been deteriorating near the bends and I want to replace the line with something more smooth to fix that and make it a little easier on the pump.

The obvious is to use schedule 80 PVC pipe with long radius bends. BUT when I look at plumbing supply places, schedule 80 PVC does not tend to come with long radius bends. However, I can buy schedule 80 PVC for electrical conduit much more cheaply and I can buy long radius 90 degree and 45 degree bends that would be perfect for what I am doing.

Of course using light schedule 40 pvc for plumbing is not ok for electrical. But I see no reason why I cannot use schedule 80 electrical conduit PVC for this low pressure plumbing drain pipe application. Do you guys see any holes in this? I am pretty sure schedule 80 PVC is schedule 80 PVC and a smooth pipe is a smooth pipe. Interior joints in the electrical version should be just as smooth or better and the material just as strong.

I will also likely wrap the outside portion of the pipe with pipe wrap tape to shield from the sun (probably the main issue for PVC relative to cast iron) and provide a little more vibration damping beyond the pier anchors (every ~4 ft up the hillside). If the expanded **** connectors often incorporated in schedule 80 pvc are an issue, I could cut those off and use standard straight junctions.

Maybe the main issue is dumb inspectors. If inspected, one might see electrical pvc and flip out. BUT a confession. I do a huge amount of work (plumbing, electrical, structural, ...) 98% ignoring inspections since I do all from A-Z. My experience in Cali is that it is too much trouble to go through the process and the dummies often want to call and engineer for anything nonstandard. Then the engineer does nothing other than charge large fees.

What do you guys think. Am I missing something? Know any source of large radius schedule 80 plumbing PVC fittings? I could find none and tight bends would certainly be worse.

Sorry ... put this in tools by accident (no plumbing section). I do not see how to move it (fabrication?). But maybe this is better since this section gets more general people commenting.

I think that it will work if you do it as described; a good coat of paint will hide a lot.

 

[P0234]

It'll probably work, but as you say, if an inspector sees it, he'll get a huge woody and feel like he made his pay for the month.

 

[mike93lx]

In a low pressure application, the electrical stuff should actually be better (code aside) since it is uv resistant already.

But if this is in the sun, expansion and contraction will be an issue. How are you dealing with that?

 

[lund]

In a low pressure application, the electrical stuff should actually be better (code aside) since it is uv resistant already.

But if this is in the sun, expansion and contraction will be an issue. How are you dealing with that?

That is a very good good point. Thanks.

Yes, much of the pipe run on the hillside is in the sun and even in northern Cali a rare hot day can be pretty hot. Pipe wrap can mitigate some of the heating issue, along with the fluid (ack ... sewer water) in the pipe since it remains mostly filled between cycles. But there would be some temp motion. The main issue there is that might stress the end run joints and fittings (where it threads into an end box/valve at top likely worst). I do not think plastic does well with stress over long periods. Cast iron also thermal expands as anything does, but to a lesser degree, and it has higher mass (less motion in pump cycles) and likely much stronger thread fittings at the end.

I can think of a solution to this: At the top of the run near where the pipe goes into the sewer, put a PVC expansion joint. This would allow some small motion with temperature changes to relieve stress. Example:

https://www.menards.com/main/electr...-coupling/bpf006h/p-37325794906558-c-9538.htm

At the top this would be very low pressure and this type of joint would be unlikely to leak for a long time. Even if it did the leak, the problem would be outside and likely small.

The pipe will be 3" in diameter.

 

[lund]

It'll probably work, but as you say, if an inspector sees it, he'll get a huge woody and feel like he made his pay for the month.

Exactly.

I rebuilt the house heavily with almost no inspections ... but to better than code (I tend to overdo things and my time spread out is free to me). The house is now rented and I am not local. So my main worry is IF something ever goes wrong and I cannot travel on short notice, then a trades man/plumber might get called for a repair. Then IF (my observations is trades men do not appear to inspect much in repairs) the tradesman contacts an inspector, then the inspector may notice mods that are not engineer certified and go ape over it. So this highlights my need to do things well and avoid any snafu issues.

Parenthetically, the whole California system of home inspections seems like an annoyance tax. They make you do that on sales/loans. I guess if someone knows little or nothing, the system is a plus. But yikes, the inspectors that I met do little other than collect fees and did not impress me at all. They definitely tend not to be New England craftsman types. Most to not appear knowledgeable on hillside home issues and just want to call in engineers who then do nothing if they think you are competent. So it ends up a annoyance tax.

I am a scientist/engineer by trade (different field). I do not mind paying for real competent advice, but in my experience the plan and inspection process just does not work. Feedback here (thanks Garage Journal) and similar places tends to be more useful for ideas to solve issues.

 

[gsmith22]

i haven't read the whole thread so sorry if this was covered already, but regular white scho 40 PVC in my experience is a lot more UV resistant than the grey electrical conduit. There are literally thousands of exposed white pvc pipes in everyone's backyard with a pool. In my own experience, with my pool, the exposed white PVC looks no different than the day it was installed but the exposed grey electrical conduit has turned a deep burgandy color in a few areas that get direct sun. plus there is specifiic pvc paint if you really want to make any pipe uv resistant

 

[mike93lx]

That is a very good good point. Thanks.

Yes, much of the pipe run on the hillside is in the sun and even in northern Cali a rare hot day can be pretty hot. Pipe wrap can mitigate some of the heating issue, along with the fluid (ack ... sewer water) in the pipe since it remains mostly filled between cycles. But there would be some temp motion. The main issue there is that might stress the end run joints and fittings (where it threads into an end box/valve at top likely worst). I do not think plastic does well with stress over long periods. Cast iron also thermal expands as anything does, but to a lesser degree, and it has higher mass (less motion in pump cycles) and likely much stronger thread fittings at the end.

I can think of a solution to this: At the top of the run near where the pipe goes into the sewer, put a PVC expansion joint. This would allow some small motion with temperature changes to relieve stress. Example:

https://www.menards.com/main/electr...-coupling/bpf006h/p-37325794906558-c-9538.htm

At the top this would be very low pressure and this type of joint would be unlikely to leak for a long time. Even if it did the leak, the problem would be outside and likely small.

The pipe will be 3" in diameter.

I can't imagine using an expansion joint in a plumbing application, especially sewage.

Can you bury the line to keep the temp more consistent?

 

[lund]

I can't imagine using an expansion joint in a plumbing application, especially sewage.

Can you bury the line to keep the temp more consistent?

I have reservations about it also. But at the top of the pipe the pressure is almost nil (just splash flow over flapper valve) and the joint has O-rings.

The expansion length with sun exposure would be about 25' max. So I doubt it would be much motion: the expansion coefficient of PVC is ~3.38 x 10^(-5) in/in/degF . So with 25' = 300" and a 70 deg max swing (30 deg to 100 deg F) that would be a motion of 0.79 in. These are all upper bounds. But that is enough where it is likely wise to deal with to avoid a stress break at a fitting.

Unfortunately, the hillside is an irregular 45 degree run and it would be hell to trench. There are also piers with tiedowns there for the present cast iron pipe.

By the way, cast iron has an expansion coefficient of 5.8 x 10^(-6) in/in/degF ... so about 10x less. So that is a big plus for metal along with the mass (less likely to move with fluid slosh on pump cycle). So cast iron likley only moves ~0.1 in max bound.

 

[lund]

i haven't read the whole thread so sorry if this was covered already, but regular white scho 40 PVC in my experience is a lot more UV resistant than the grey electrical conduit. There are literally thousands of exposed white pvc pipes in everyone's backyard with a pool. In my own experience, with my pool, the exposed white PVC looks no different than the day it was installed but the exposed grey electrical conduit has turned a deep burgandy color in a few areas that get direct sun. plus there is specifiic pvc paint if you really want to make any pipe uv resistant

I could certainly paint first and tape it for more resistance. I am not so worried about uv since that can be dealt with. The larger issue is likely line fitting stress from thermal expansion of the PVC (see above).

 

[BrandonV]

Always use the PVC expansion fitting... I redid my irrigation system in PVC and even underground (an inch or two) the temperature changes have caused it to pop up in places.

 

[lund]

Always use the PVC expansion fitting... I redid my irrigation system in PVC and even underground (an inch or two) the temperature changes have caused it to pop up in places.

I can see the point for longer runs based on the PVC expansion coefficient estimate I put above. For a long thin pipe that has some freedom of side motion slop, it may be ok. But if a more rigid thick walled pipe tied down well at the ends and anchored periodically, I can easily see it will generate expansion and/or contraction stress. I am surprised small (?) irrigation pipes underground were a problem for you. But in my case for for a thicker and short schedule 80 rigid pvc pipe length with sun exposure and anchors every few feet, I can easily see the need. I also need the anchors since the fluid volume moving via the pump (3" diameter pipe) is significant.

 

[kngelv]

Some of the posts on here blow my mind. Another guy who thinks he knows better than everyone else and that inspectors are useless yada yada yada.

James

 

[mike93lx]

I can see the point for longer runs based on the PVC expansion coefficient estimate I put above. For a long thin pipe that has some freedom of side motion slop, it may be ok. But if a more rigid thick walled pipe tied down well at the ends and anchored periodically, I can easily see it will generate expansion and/or contraction stress. I am surprised small (?) irrigation pipes underground were a problem for you. But in my case for for a thicker and short schedule 80 rigid pvc pipe length with sun exposure and anchors every few feet, I can easily see the need. I also need the anchors since the fluid volume moving via the pump (3" diameter pipe) is significant.

I haven't heard about an expansion joint being used in an irrigation system before

 

[BrandonV]

I haven't heard about an expansion joint being used in an irrigation system before

I have some long straight runs that are only an inch or two under the dirt.

Combine that with 110F+ heat I can see movement.

Still better than that crappy plastic distribution tubing.

 

[mike93lx]

I have some long straight runs that are only an inch or two under the dirt.

Combine that with 110F+ heat I can see movement.

Still better than that crappy plastic distribution tubing.

I was going to ask about aerating, but saw you live in AZ, so I'm guessing this isn't for a lawn?

 

[BrandonV]

I was going to ask about aerating, but saw you live in AZ, so I'm guessing this isn't for a lawn?

Nope. Just drip irrigation.

Dogs, the sun, etc. The poly mainline tubing is irritating to work with and fails all the time. I just go PVC all the way to the tree/bush/whatever and then T off to a manifold or a barb fitting for the 1/8" distribution tubing.

 

[lardy1]

Maybe a rubber connector interspersed rather than rigid couplings would compensate for whatever expansion it does encounter. Is this in Michigan? If so, what keeps it from freezing?

 

[lund]

Some of the posts on here blow my mind. Another guy who thinks he knows better than everyone else and that inspectors are useless yada yada yada.

James

Sure James. Whatever you say. I was asking for opinions and I got immediate help on target on something that I overlooked. Then i replied right back with thanks and a confirming estimate. Filtered help here can be quite good.

Let me guess. You an inspector? No disrespect was intended. But my limited interactions with inspectors in cali have not been good with hillside home matters (many special cases). I am a research scientist and engineer. I do not get the impression the ones I dealt with are capable of design. I hope that I had a bad sample on small number statistics. But if not, the group can be alarmingly inept.

 

[lund]

Maybe a rubber connector interspersed rather than rigid couplings would compensate for whatever expansion it does encounter. Is this in Michigan? If so, what keeps it from freezing?

House is near san fran but I live in michigan now and do fixes/upgrades on semi regular trips.

Something like you suggest could work but I would worry about slips and leaks.

Usually bellows (pipe with accordian tube like section) are used for pipes in industrial stuff to account for thermal length changes. But such can be expensive and troublesome.

The part I linked above will likely work for what I am doing but not for much pressure.

 

[ycgoat]

I am not sure what the difference between electrical PVC and plumbing PVC, but electrical PVC typically lets water in the conduit at the joints, even when primed and glued

 

[Doc_Possum]

I used electrical PVC for my pool plumbing for two reasons... large radius elbows and the grey color. 3 years later it's been working great. Regular PVC fittings work on it too.

 

[mike93lx]

I am not sure what the difference between electrical PVC and plumbing PVC, but electrical PVC typically lets water in the conduit at the joints, even when primed and glued

That's an installation issue, not a pipe issue.

 

[lardy1]

These hold up to the pressure of my sewage ejection pump. They've never leaked or given any indication that they might fail.

 

[CraigStu]

Outside I'd rather have the expansion joint w/ internal o-rings than the rubber couplings. The o-rings at least are mostly shielded from sun etc. If there are more than one 0-ring the outer could be considered the shield while the inner could be considered the seal.

 

[lund]

These hold up to the pressure of my sewage ejection pump. They've never leaked or given any indication that they might fail.

Cases and context. I suspect you are fine. But my situation, unfortunately, is likely more extreme with a very long run and steep rise that is part outside. For short runs and smaller pipes schedule 40 PVC (white) is probably fine and fittings (elbows, values, etc) are available in a lot of variety in many stores. But in my case, the run is a 3" pipe with a ~35' rise and ~50' run. That is a lot of fluid motion and a big pump. The pressure is not that high outside of fluid pressure on the low end, but the mass of water/sewage moving in the pump cycle is big. When pump cycles start and stops there is vibration and a big momentum transfer. So a heavier (schedule 80 PVC and/or cast iron) is desirable along with a lot of anchors. Unfortunately, plumbing schedule 80 PVC does not appear to be as readily available in large radius bends (45 and 90 deg). Or at least I could not find any. However, schedule 80 conduit PVC should be the same strength and is readily available in big box stores with large radius bends and much cheaper. So I think I will go that direction.

Probably the main issue for me will be getting proper strain relief for a longer plastic pipe in the sun to allow for thermal expansion and contraction. I will likely adjust the anchors to allow longitudinal motion and put an expansion joint at the top (where lowest pressure). I will also do something to protect the pipe from UV (paint and pipe tape) and dampen vibration.

I appreciate all the input. It helped me avoid a likely blunder.

 

[RegeSullivan]

I am not sure what the difference between electrical PVC and plumbing PVC, but electrical PVC typically lets water in the conduit at the joints, even when primed and glued

Not an expert on the subject but I suspect the majority of water in buried conduits is condensation.

 

[larry4406]

Can you use an E-One style grinder pump which uses 2” SCH80 pipe and run this PVC inside your existing arial 3” cast iron?

 

[dcg9381]

I learned about PVC expansion fittings from you guys.. I haven't seen them in residential very often here.

I may or may not have used 3" electrical PVC sweeps in several locations for "exit the foundation" drains in a building that I wouldn't call "residential class". I like to put drains in every corner of a shop "just in case" for a 2nd story redesign.

 

[lund]

Can you use an E-One style grinder pump which uses 2” SCH80 pipe and run this PVC inside your existing arial 3” cast iron?

That might work, in principle, to shield the pipe and keep temps more uniform.

But I have two (one spare one installed) very expensive, high power grinder pumps to deal with the very high rise (~35') of this application. The original design has the pump (I think 2" exit line) filling a 3" cast iron pipe (transition right after lower valve) going up the hill with a few bends near the low end before a straight shot going up the hill. The bends are also 3". So yes, I *maybe* could get 2" pvc in the cast iron pipe up the hill ... but no way threading the bends. I also do not think that would be wise to drop pipe diameter from present 3" to 2" due to the clog potential with the smaller diameter and the nonstandard aspect (any inspector could truly have a cow with a drain pipe within a drain pipe!).

 

[finn]

Isn’t that what the green (pvc?) plastic pipe with the gasketed joints for? I’m no plumber, but I commonly see green pipes with some sort of elastomeric seal being used. The pipes may not be available in 3” diameter, but I’m pretty sure I have seen them in 4” and larger diameter, and being used for sewage, not potable water, although I might not have that correct, as I didn’t pay particularly close attention.

We were having root incursions in our run to daylight foundation footing drains and gasketed pipe was suggested by a guy who does building, including plumbing, for a living.

In any event, I don’t see a reason to go outside code guidelines, which probably means no electrical conduit for sewage.

 

[mike93lx]

Isn’t that what the green (pvc?) plastic pipe with the gasketed joints for? I’m no plumber, but I commonly see green pipes with some sort of elastomeric seal being used. The pipes may not be available in 3” diameter, but I’m pretty sure I have seen them in 4” and larger diameter, and being used for sewage, not potable water, although I might not have that correct, as I didn’t pay particularly close attention.

We were having root incursions in our run to daylight foundation footing drains and gasketed pipe was suggested by a guy who does building, including plumbing, for a living.

In any event, I don’t see a reason to go outside code guidelines, which probably means no electrical conduit for sewage.

Green is thin wall, drain/waste pipe, not rated for pressure. Wouldn't be good for this application and would likely fail

 

[Youngandfree]

If it's a low pressure drain line, why would a normal 90 be such a problem to start with?

 

[lund]

Isn’t that what the green (pvc?) plastic pipe with the gasketed joints for? I’m no plumber, but I commonly see green pipes with some sort of elastomeric seal being used. The pipes may not be available in 3” diameter, but I’m pretty sure I have seen them in 4” and larger diameter, and being used for sewage, not potable water, although I might not have that correct, as I didn’t pay particularly close attention.

We were having root incursions in our run to daylight foundation footing drains and gasketed pipe was suggested by a guy who does building, including plumbing, for a living.

In any event, I don’t see a reason to go outside code guidelines, which probably means no electrical conduit for sewage.

I would happily buy heavier 3" diameter schedule 80 PVC fittings for plumbing IF they were available. I do not think they are, or at least I could not find such in stores or online orders. But my search was not exhaustive. What is missing: large radius 90 deg and 45 deg elbows and expansion joints. If anyone knows a source for such, please let me know.

Schedule 90 PVC for conduit and drain pipes should be identically the same material. I suspect it is from the same industrial sources. So the logic of using the conduit and plumbing pipes only for the respective applications is probably not sound. However, that does not mean an inspector would be happy about it IF they notice (which might be hard if pipes are painted/covered for UV protection in external locations and short sections inside I could easily avoid using labeled sections.

 

[LOW1]

At our cabin we pump septic waste up a hill to the septic tank using red line irrigation pipe. Comes in long rolls and uses barbed fittings. Heat the pipe with a torch stick the fitting in and it seals down.

We use the same pipe to pump in water from the lake for drinking etc.

Code approved here

 

[lund]

If it's a low pressure drain line, why would a normal 90 be such a problem to start with?

The pipe is attached to a very large sewer ejector/grinder pump with a ~35' vertical rise over a ~50' run. When you have a tight elbow it increases the resistance to flow so the pump has to work harder. It also increases concern over debris (sewer water ... though the pump grinds also) collecting and restricting flow in the elbows. So it is best to have large radius bends. Well anchored, heavy pipes are also desirable since the motion of the water and the pump creates vibration and stress. So either heavy PVC (Schedule 80, usually grey rather than white used to flag ordinary Schedule 40 PVC) or cast iron pipe is preferable. Joints in cast iron can be a problem (seals degrade and vibration can deteriorate neoprene style interconnects over years). So I would like to go with schedule 80 PVC.

Unfortunately, plumbing schedule 80 PVC elbows (45 deg and 90 deg) do not appear available in long radius (sweep) style -- or at least I have been unsuccessful in finding a source. But conduit schedule 80 PVC may be essentially the same other than the label on it and readily available in the needed types (with long radius bends) and is also much cheaper (presumably due to high sales volume).

 

[BombShelter]

Long thread, sorry I didn't read most of it.

If Spears or George Fisher doesn't make it, it probably doesn't exist.

Spears Manufacturing, PVC & CPVC Plastic Pipe Fittings & Valves

ISO9001 Certified - PVC & CPVC Sch 40 and 80 fittings molded from 1/8 - 14 inch.

www.spearsmfg.com

Industrial Schedule 80 PVC Piping System - GF Industry and Infrastructure Flow Solutions

www.gfps.com

These are the two heavy-weights for plastic piping and fittings. They should be available locally (or the distributor can get the part within a few days). They also have design guides for long runs of pipe to account for expansion/contraction.

Most PVC can be painted with latex if heat or UV is a concern.

 

[lund]

Long thread, sorry I didn't read most of it.

If Spears or George Fisher doesn't make it, it probably doesn't exist.

Spears Manufacturing, PVC & CPVC Plastic Pipe Fittings & Valves

ISO9001 Certified - PVC & CPVC Sch 40 and 80 fittings molded from 1/8 - 14 inch.

www.spearsmfg.com

Industrial Schedule 80 PVC Piping System - GF Industry and Infrastructure Flow Solutions

www.gfps.com

These are the two heavy-weights for plastic piping and fittings. They should be available locally (or the distributor can get the part within a few days). They also have design guides for long runs of pipe to account for expansion/contraction.

Most PVC can be painted with latex if heat or UV is a concern.

THANK YOU !!

Yes, Spears appears to have plumbing approved 3" PVC expansion joints and long radius schedule 80 bends (90 deg but curiously did not see 45 degree and other angles for less than 4" diameter).

Spears prices are shocking though: $186 for the 3" 90 deg bend I can get in conduit form for about $30 and $1,500 for an expansion joint that I can get in conduit form (though this one may differ with the o-ring seals to better fit plumbing) that I can get for about $70. So more industrial pricing where cost may be less of an issue.

Plumbing parts are always such fun ... But it is good to see there are sources.

 

[Youngandfree]

The pipe is attached to a very large sewer ejector/grinder pump with a ~35' vertical rise over a ~50' run. When you have a tight elbow it increases the resistance to flow so the pump has to work harder. It also increases concern over debris (sewer water ... though the pump grinds also) collecting and restricting flow in the elbows. So it is best to have large radius bends. Well anchored, heavy pipes are also desirable since the motion of the water and the pump creates vibration and stress. So either heavy PVC (Schedule 80, usually grey rather than white used to flag ordinary Schedule 40 PVC) or cast iron pipe is preferable. Joints in cast iron can be a problem (seals degrade and vibration can deteriorate neoprene style interconnects over years). So I would like to go with schedule 80 PVC.

Unfortunately, plumbing schedule 80 PVC elbows (45 deg and 90 deg) do not appear available in long radius (sweep) style -- or at least I have been unsuccessful in finding a source. But conduit schedule 80 PVC may be essentially the same other than the label on it and readily available in the needed types (with long radius bends) and is also much cheaper (presumably due to high sales volume).

2 45 elbows will make a longer 90.

 

[lund]

2 45 elbows will make a longer 90.

Just a little bit due to the connection sections. The bend radii (I think) will be the same at the 90 deg. So the resistance to flow issue will likely not change much.

Thanks!