Grand Banks Fresh Water Piping

[Mac G]

What are the inside and outside diameters of the original black plastic fresh water plumbing hoses/pipes used on the Grand Banks?

They appear to be 1/2 inch, but maybe slightly different.
Do conventional modern sharkbite fitings work on those?

Do conventional pipe thread fittings work with the GB fittings?

Please advise

Thank you

[stiggy]

Do you have pictures?
Ours is a '95 and has grey "Qest” Polybutylene throughout which we are gradually changing over to pex. There is a Sharkbite PEX to Polybutylene, labeled PEX to PB. Ours is 3/4” from the tanks to pump and 1/2” from filters to point of use.

We are currently in the process of refitting this.

[wkearney99]

Most boat vendors have used an assortment of plumbing systems, varied over time. What year/model is your boat?

[SteveK]

OP What year is your boat. My GB36 1971 has black pipes. They are very close to 1/2inch ID and with a heat gun 1/2" barb fittings have worked.

[kdebelser]

Interesting. My 1980 GB36 has the black plastic which measures 0.67"od so sharkbite and the like will not work since they only work on 0.625"od. I have a leak so need to figure something out soon. Will likely try the barb. Hope this doesn't mean replumbing the whole boat!!

[SteveK]

Originally Posted by kdebelser

Interesting. My 1980 GB36 has the black plastic which measures 0.67"od so sharkbite and the like will not work since they only work on 0.625"od. I have a leak so need to figure something out soon. Will likely try the barb. Hope this doesn't mean replumbing the whole boat!!

Get a 1/2' OD fitting, I used a plastic grey barbed and then heat gun on the black, while warm clamp it tight, heat again, tighten. Test, if it leaks start over. Mine has not leaked in two years now. (still own the GB)

[Cigatoo]

So I have the gray pipe. 84 Grand Banks. I am under the impression that gray is polybutylene. What is the black? I know Sharkbite has polybutylene to Pex fittings.

[SteveK]

Originally Posted by Cigatoo

So I have the gray pipe. 84 Grand Banks. I am under the impression that gray is polybutylene. What is the black? I know Sharkbite has polybutylene to Pex fittings.

black plastic poly pipe. I thought it was way back, but Home depo sells it.

[kdebelser]

I’m not sure what the black is on my boat but it’s not the current pvc. Different dimensions. Going to try the bards as someone suggested. Failing that may have to replace it with pex.

[SteveK]

Originally Posted by kdebelser

I’m not sure what the black is on my boat but it’s not the current pvc. Different dimensions. Going to try the bards as someone suggested. Failing that may have to replace it with pex.

Remember the boat was not built on these shores, maybe metric.

[Comodave]

Originally Posted by SteveK

Remember the boat was not built on these shores, maybe metric.

Yes, or some unusual pipe used in the far east. Replumbing may be the best bet. If it is leaking in one place now it may start leaking in more tomorrow or the next day. We replumbed a 46’ trawler with SeaTech, now it is called something else, and it was really pretty easy. We special ordered straight sticks of the pipe as what WMP had in stock was in rolls. And trying to straighten it out was next to impossible. With the straight sticks we could push it through closed areas and the rolled up pipe would just curl up inside the areas.

[Bmarler]

Sounds like it could be 17mm tubing. There are fittings available, but not as good of a selection as more common sizes.