I bought a whole house water filter to hook up to the main water line. The plumber who came in said that he won't be able to install it because the pipe that comes from the ground hooked up to the copper pipe is plastic.

He says that this plastic is usually not used for that kind of water pressure for the main line and can burst at any time. If he starts cutting the pipe above it to hook up the water filter, there is a potential that the plastic could break/leak due to all the shaking etc. He has asked me to contact the builder/home inspector (as it shouldn't have passed the home inspection like that? ) and take care of this first.

Picture is below. The black color pipe is the one in question. Has anyone seen plastic pipes come up from the ground like that to the main line? Will it burst?

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Update - new pics and details

Close up pictures on request. I looked the pipe closely. It is written 1 1/2" 0.1 / Plastic. (above the first ring at the bottom, you can see it in the second pic). House is built in 1993.


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  • 2
    (side note) I'm not an expert but-- isn't grounding to those pipes kinda pointless, since it's going into a plastic pipe into the ground? Commented Sep 13, 2012 at 23:51
  • Did you read this "1 1/2" 0.1 / Plastic" off the coupling (the black piece that joins the two pipes), or the black pipe itself?
    – Tester101
    Commented Sep 14, 2012 at 11:48
  • ok, I read it on the coupling then, I couldn't see anything on the pipe itself. I'll try one more time today to check the pipe in detail.
    – coder net
    Commented Sep 14, 2012 at 16:49
  • 1
    I'd be a lot more worried about my ungrounded electrical system than the plumbing. Commented Apr 3, 2015 at 15:36

5 Answers 5


Though it may seem odd, it is possible the plumber knows what he's talking about. If this is a Polybutylene pipe, it could indeed be brittle and fail if it's jostled during the installation of the filter.

It's impossible to tell from the picture what type of pipe that is, but based on the plumbers concern I'd guess it is Polybutylene.


Polybutylene was used in pipes between about 1980-1994/5, and was commonly used as supply line in the 80's. It was found (in some cases) to react with oxidants in the water supply, which caused the pipe to become brittle and fail. To my knowledge, this type of piping is no longer used. Though if the house was built; or there was supply line work done, during the 80's, it's likely this is Polybutylene pipe.

High Density Polyethylene

Don't confuse Polybutylene pipe with Polyethylene pipe. High-density polyethylene is commonly used as water supply line today, and is stable and safe to use.

Cross-linked polyethylene

Cross-linked polyethylene (PEX) is not typically used as an underground supply line, as it can sometimes react with minerals in the soil. Where PEX is used underground, it's typically encased in sand (or other non-reactive materials) to prevent negative reactions. Because of this it's often more expensive to bury PEX, so other materials are used instead.

How can I tell what it is?

The only way to be sure what type of pipe this is, is to look for markings on the pipe itself. Polybutylene will be marked PB####, Polyethylene will be marked PE####, Cross-linked polyethylene will be marked PEX-x (where x = A, B, or C).

  • 2
    Now this is a valid point - IF it's Polybutylene, you should immediately invest in replacing the water main, before the line breaks, because its only a matter of time. (Voice of experience talking here) Commented Sep 13, 2012 at 12:23
  • @Tester101, it is marked as Cresline HD100 PE 3408. Based on your feedback, I guess it is safe? so whatever shaking/disturbance is done on the upper part for filter installation won't affect this pipe?
    – coder net
    Commented Sep 16, 2012 at 12:54
  • 1
    @codernet I'm not a fan of the rubber coupling on a pressure line, but aside from that the pipe itself should be alright. Copper is cut using a pipe cutter, so unless you have to pull the pipe away from a wall (or other obstacle) to cut it, there shouldn't be too much vibration involved.
    – Tester101
    Commented Sep 17, 2012 at 12:03

Isn't that your water meter on the inside of your house, that the black city line feeds?

Shouldn't the whole house water filter be going AFTER the water meter?

In which case the black pipe is irrelevant, is it not?

Which leads me to think - you need a different plumber.

  • 3
    Furthermore - looking at the picture more closely, the water meter is connected using a compression fitting, so all your plumber needs to do to install the whole house filter safely is shut off the main, disconnect the compression fitting by unscrewing it, then he can remove the copper from the wall by removing the mounting braces with almost no vibrations at all - and after the pipe is free of the wall he can use a tubing cutter to cut the pipe wherever he needs without shaking it as well... Commented Sep 13, 2012 at 0:24
  • 3
    Sounds like a plumber who did t want to put a filter in to me... Lol
    – UNECS
    Commented Sep 13, 2012 at 0:28
  • he may be afraid of the weight of the meter snaping the pipe and or bumping it etc.
    – Kendrick
    Commented Sep 13, 2012 at 2:50
  • @Kendrick The meter connects on both ends - the same way too - simple solution there would be disconnect the intake line first. Commented Sep 13, 2012 at 12:25
  • What he said is that if he cuts the copper pipe above, it may shake this plastic, and he just does not want to cause any probable damage and cause a leak later. He said he can do it but its not advisable for me.
    – coder net
    Commented Sep 14, 2012 at 1:01

Yes, it's common. In fact, nearly all modern residential construction uses plastic PEX piping (and it's widely considered superior to copper).

Now, perhaps your plastic pipe is wrong... but that would be interesting as it's no simple task to replace an entire water main... Can you take a better photo of the plastic pipe?

  • 5
    Not all plastic pipe is PEX.
    – Tester101
    Commented Sep 13, 2012 at 12:22
  • 1
    I also disagree that nearly all modern construction uses PEX. While it's popularity is on the rise, many installers still prefer CPVC (rigid, uses lots of connecting fittings) or copper (expensive, tends to get stolen). PEX is distinctive in that it's a flexible line that requires no elbow joints or connectors every 8' - but its new, so many plumbers are dubious about it (without cause IMO - just dislike change cause, you know, its different...) Commented Sep 13, 2012 at 12:44
  • @Tester101 this is true, but I find that usually when people say "plastic pipe" in-wall residential they are talking about PEX.
    – Matthew
    Commented Sep 13, 2012 at 15:01
  • @TheEvilGreebo PEX isn't new, it's just newer in this area. There was, likewise, a time when some "old-school" builders refused to use plywood. IMHO the resistance to PEX often comes from people who are simply uncomfortable working with it. The point of my post is that it is most definitely not a cause for concern, and is quite common and is not dangerous.
    – Matthew
    Commented Sep 13, 2012 at 15:04
  • It is new, relative to the age of the plumbers out there working with it. Just got to any big box store and see how much PEX components don't fill the shelves compared to copper and PVC. Commented Sep 13, 2012 at 15:15

That looks very similar to the plastic pipe the brings water into my house. Depending how much is visible, you may be able to find some writing that will tell you more about it. Different pipes that look similar may be rated for different PSIs. Ours had a couple of leaks out in the ground and was rated for (iirc) 100psi. The new pipe that we had put in looked almost identical but was a little thicker and rated for 200psi.

The guys that did my line replacement told me that the older stuff was ok for wells but city psi is much higher and also that in the city, the psi raises at night and other times when there is less demand.

Realistically, I'd get a 2nd opinion. I don't see any reason why turning the water off and installing a whole house filter would compromise the existing stuff. Once you turned the water off, you'd disconnect one of the unions going to the plastic pipe, so you aren't going to wiggling on the plastic pipe at all anyway. It may be a legitimate concern, but it might also be that he didn't want to be on the hook for issues that you may have later down the line. Did it seem like he was trying to convince you to replace the supply line, or just talk you out of installing a filter?

  • He said he does not have a problem installing the filter. But it is possible that we could accidentally damage the set up due to cutting pipe/shaking etc and he does not want to be responsible for any damage. SO it is in my best interest to get that fixed first and then install the filter.
    – coder net
    Commented Sep 14, 2012 at 1:08

no way to tell from the picture. if that is sched40/80 rigid plastic pipe like what that white pipe is he may well be right. most mobile homes and some new instals use a unerground raited pex like pipe that is armored and made to go in the ground. if they put rigid plastic that is likely to get destroyed even by tree roots. you find that out after your first 2k water bill...

  • It doesnt look like it it looks more like pe which is even used for underground sewer mains etc judging by the curve in the pipe it isn't ridge like the PVC pressure pipe other wise the fitting would be of a different type as well
    – UNECS
    Commented Sep 13, 2012 at 3:49
  • unecs after moving in to my house I have learned to assume nothing. slightly melted and warped pvc giving it the not straight look as shown in the photo, a 45 shell capping the ice maker take off... Since we dont have identification markings clearly visible who knows.
    – Kendrick
    Commented Sep 13, 2012 at 22:32

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