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Old 10-13-2021, 01:28 AM   #1
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Splicing domestic water hose

Our 1981 36CL has the original rigid black plastic domestic water piping. Fearful of opening a can of worms over the years I have avoided tampering with it. However there are some projects I would like take on which mean cutting into the pipe. I really do not want to re plumb.
Are there fittings available (I think of Shark bite) which allow adding Pex hose for instance.

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Old 10-13-2021, 02:14 AM   #2
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Welcome aboard. I absolutely hate working on plumbing since I am not good at it and it always leaks. But with Shark Bite fitting you will probably ba able to do what you need to. Before you cut any I would get an accurate measurement of the OD and go to a real plumbing store and ask if they have fittings that will work. Good luck.
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Old 10-13-2021, 03:08 AM   #3
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Yes, measure twice, cut once and get the right fitting. And know it it's mm or inches. There are several sizes that are so close it's hard to tell them apart. In a lot of water systems, it's common to find 15mm tubing and 1/2 fittings in the same system.

As for finding a good plumbing store that knows there stuff... good luck. Those guys are disappearing. Ain't gonna find it at Home Depot. I've had better luck calling the techs at the manufacturer.


I could make an argument, if adding a line, to replace it with SeaTech. However, sometimes you just can't find a fitting or part that makes it compatible and have to use a Fernco fitting to make it work.


SeaTech tech support is very good.
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Old 10-13-2021, 06:54 AM   #4
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Hi, When working with that black ridgid tubing on a friends older GB we found intalling hose barb adapters to allow the use of Pex was a lot easier when we gently warmed the open end of the black pipe with a heat gun. It slightly expanded and softened allowing a 1/2 barb adapter to slide right in. Once cooled a hose clamp completed the job. These connections never leaked for us. John P
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Old 10-13-2021, 06:03 PM   #5
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Thanks for the responses. Iím now not so worried. The plan is to add a mixing valve. Are there any hard lessons I might avoid with that?
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Old 10-13-2021, 10:26 PM   #6
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I have made modifications into that black pipe. I used barbed fittings after considering shark bites. I did not take measurements of the ID, just went ahead and used what I had available, no leaks after a year or so. I will guess it was 1/2 inch ID. maybe 3/8. Point is regular available stuff works.
Use heat gun on the hose to soften before inserting the fittings and hose clamp before it cools completely.
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Old 10-14-2021, 10:43 AM   #7
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That grey plastic pipe from the early 80's is Qest. (No "u.") Don't assume a SharkBite or other fitting will work unless it says so on the package.

The good news is that stuff is pretty easy to work with. They are designed to be connected finger tight. Stop when you hear a squeak. All the threaded fittings are standard threads, so you can replace any section with newer products. And you can still buy the Qest fittings if you want.

Qest got a very bad name from failures in homes inside walls. I'm not sure about the details, but the Qest fittings in my 1980 boat have held up just fine. I've upgraded to PEX in places where I've added or made major changes, but I have found no reason to take out what's been working well for over 40 years now. In fact, those hand-tighten connections make it easy to winterize the potable water system. I just pull the connection at the bottom of the tank and stick the hose into a bottle of antifreeze. Try that with SharkBite connections!
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Old 10-14-2021, 12:15 PM   #8
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That grey plastic pipe from the early 80's is Qest. (No "u.") Don't assume a SharkBite or other fitting will work unless it says so on the package.

The good news is that stuff is pretty easy to work with. They are designed to be connected finger tight. Stop when you hear a squeak. All the threaded fittings are standard threads, so you can replace any section with newer products. And you can still buy the Qest fittings if you want.

Qest got a very bad name from failures in homes inside walls. I'm not sure about the details, but the Qest fittings in my 1980 boat have held up just fine. I've upgraded to PEX in places where I've added or made major changes, but I have found no reason to take out what's been working well for over 40 years now. In fact, those hand-tighten connections make it easy to winterize the potable water system. I just pull the connection at the bottom of the tank and stick the hose into a bottle of antifreeze. Try that with SharkBite connections!
I thought the grey pipe used in the GB was polybutylene? Or is that the same as Qest? SharkBite has polybutylene to Pex fittings that I had hoped to use when the time comes.
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Old 10-14-2021, 02:32 PM   #9
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Thank you Capt Tom...very interesting. If the treads are standard then I should be able to just splice in the short lengths of Pex that I need assuming I can still obtain the fittings?

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Old 10-14-2021, 05:15 PM   #10
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If it is the grey pollybutal pipe you can get a pex adapter for it there are 2 different crimp rings. I removed all of this pipe on our boat and went back with pex. We had several issues none causing damage and pex is super easy to work with. Lowes and home depot sell the transition fittings
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Old 10-14-2021, 05:23 PM   #11
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Thank you Capt Tom...very interesting. If the treads are standard then I should be able to just splice in the short lengths of Pex that I need assuming I can still obtain the fittings?
A picture is worth 1,000 words...

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Old 10-14-2021, 06:08 PM   #12
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A picture is worth 1,000 words...

Nice work and nice clean bilge
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Old 10-14-2021, 06:10 PM   #13
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If it is the grey pollybutal pipe you can get a pex adapter for it there are 2 different crimp rings. I removed all of this pipe on our boat and went back with pex. We had several issues none causing damage and pex is super easy to work with. Lowes and home depot sell the transition fittings
Thanks
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Old 10-14-2021, 06:29 PM   #14
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My 1990 GB49 uses a gray pex according to the stamping on the tubing. I have use the 1/2 inch pex with the compression fitting to fix several minor leaks. The leeks we caused by the original aluminum compression rings touching the copper bonding strap which caused the ring to crack/break at the contact point. The remaining aluminum ones were in good condition. The new compression rings which are available at lowes solved the problem along with lots of different fittings and tubing.---- easy stuff to work if you have the compression tools.
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Old 10-14-2021, 07:13 PM   #15
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Although Iíve been a TF member for years, I did not actively participate , instead concentrating on IAGBO. When it dissolved I wandered aimlessly!! The response to my post has been so encouraging and confirms my faith in GB owners. Thanks guys. And Capt Tom your photo indeed says it all. I certainly envy the state of your engine room. Iíll never get there.

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Old 10-14-2021, 07:36 PM   #16
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I have been a TF member for quite a while but not an active participant, instead focussing on IAGBO. When it went dissolved I wandered aimlessly!!! Your responses to my post are really encouraging. Thanks guys.

And Capt Tom the photo says it all but also the standard to which most of us can only dream. Wow.

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Old 10-14-2021, 08:43 PM   #17
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Please keep in mind "Shark bite" and other press on fittings are intended for use in residential buildings. Under vibration tests the components that grip the pipe and hold it in place will cut into the tubing. I have installed them in boats and motorhomes both with NO problems. But was informed by the manufacturer that they should not be used in an application that would expose the fittings to extreme vibrations. I have had no leaks in any of my installations. ALSO a residential water pump vibrates like crazy and the manufacturer says that they are OK for use on residential water pumps. I honestly feel the products were not tested and approved for marine or motorhomes so they can not recommend for such. That being said your installation is absolutely lovely and a work of art to be proud of.
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Old Yesterday, 07:40 AM   #18
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Please keep in mind "Shark bite" and other press on fittings are intended for use in residential buildings. Under vibration tests the components that grip the pipe and hold it in place will cut into the tubing. I have installed them in boats and motorhomes both with NO problems. But was informed by the manufacturer that they should not be used in an application that would expose the fittings to extreme vibrations. I have had no leaks in any of my installations. ALSO a residential water pump vibrates like crazy and the manufacturer says that they are OK for use on residential water pumps. I honestly feel the products were not tested and approved for marine or motorhomes so they can not recommend for such. That being said your installation is absolutely lovely and a work of art to be proud of.
Ah, yes, extreme vibrations. If your boat is producing extreme vibrations, enough so that the plumbing is also vibrating extremely, then you have problems way more than a plumbing issue. I have a pair of Lehman 120s known to shake a bit at idle. Yes, a bit of vibration but extreme (?), not even close.
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Old Yesterday, 09:13 AM   #19
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And Capt Tom the photo says it all but also the standard to which most of us can only dream. Wow.
That picture was taken right after I'd installed the new water heater, before which I'd pulled the old tank and the plumbing in that area and painted. Believe me, there are parts of my ER that I'm not as proud of.

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Please keep in mind "Shark bite" and other press on fittings are intended for use in residential buildings. Under vibration tests the components that grip the pipe and hold it in place will cut into the tubing.
I'd heard that too, and since that picture was taken I've invested in a PEX crimping tool. One of the better investments I've made. Some of those SharkBite fittings in the photo have already been removed, and I'll be re-working that area again in an attempt to mitigate the pump noise. It's right behind the V-berth bulkhead and if we run the water at night it'll wake anyone sleeping there. Anyway, I've had no problems with the SharkBites but I am going to limit their use to only those fittings which need to be removable going forward.
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Old Today, 11:06 AM   #20
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I honestly feel,,,,, that the shark bite fittings were tested under conditions for residential use and not for rv or marine use. Vibrations such as hitting potholes or going over waves were not in the test conditions. We as consumers have assumed the risk of incorporating products into our systems and testing them for the company. Like I said I have had NO leaks in any of the builds I have undertaken. Also as was brought up most boats don't vibrate as much as a residential deep well pump. Shark bite's rep said that the fittings were fine for a direct connection into the cast iron pump. I have used Pex crimp also in residential applications, that was the first step in making plumbing a job tbat more people could take on. The crimper is an investment, but the rings are reasonably priced. Shark bites are up there in price but make the job easy. Doing some math in my head... a hand full of 3/4 or 1 inch shark bites would pay for a pex crimper. I am sure I speak for many when I say we would love to see pictures of your updated system when you get it completed. Your work is inspirational.
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