Thread: PP-R pipe - the green stuff

I must admit I used blue pipe for my multi-point heater in my original house in CM

7 years on and it is still fine

blue is OK as long as it is accessible, just to make sure

Isn't the problem of using blue pipe for hot water that the pipe will sag more on long, unsupported runs?

I'm going to use green pipe to connect some rooftop solar water heaters to the guestroom shower mixer - so that special tool will be available for loan in Phuket

Simon

Simon

The tool only does upto 30mm ends, so blue for cold with access. got it!

Originally Posted by Simon43

Isn't the problem of using blue pipe for hot water that the pipe will sag more on long, unsupported runs?

well, it always needs supporting, every metre or so

Some information about the different plastic resins used to produce such pipe.

Polyvinyl chloride - Wikipedia, the free encyclopedia

Polypropylene - Wikipedia, the free encyclopedia

With regard to using these resins for applications such as water pipes it's all about the given plasticizing temperature meaning when the structure starts to change from a solid mass into a liquid when exposed to heat.

Originally Posted by oldgit

See your plumber and hire it by the day, pity there's no plant hire places in LOS

There is/was one on Sukhumvit Soi 24 in Bangkok.

Originally Posted by benlovesnuk

I must admit if i could loan the tool i would get the green

I would've though borrowing the tool would be more useful?

Originally Posted by Loy Toy

With regard to using these resins for applications such as water pipes it's all about the given plasticizing temperature

I think that would be well above the boiling point for water though

Originally Posted by DrAndy

I think that would be well above the boiling point for water though

Polypropylene starts to soften, change from a solid mass into a liquid at 158 degrees Celsius. It's processing temperature, depending upon the grade of PP is between 220c and 250c. There are many different grades of PP and used depending upon it's application.

We use PP exclusively for our packaging as it has a great impact resistance, has good top load strength is fairly cheap and performs well at high and low temperatures.

This plastic also changes it's molecular structure (glass transition) at minus 8 degrees Celsius if you drop the container it will crack like glass.

That's why some plastic pipe cracks when subjected to very low temperatures.

so the pipes would be Ok for hot water

that's good

Originally Posted by DrAndy

so the pipes would be Ok for hot water

If the water is not very hot, OK
You should be thinking about the joints not the pipe.

I have watched someone place a glued PVC joint into boiling water and pull it apart.

unless you have a solar panel, the water will not be even near boiling in most domestic hot water situations

yes, the joints would be the weak point, not the pipes, so they have to be properly "glued"

Originally Posted by Thetyim

I have watched someone place a glued PVC joint into boiling water and pull it apart.

Some plastics can expand by 5% across it's diameter when subjected to a temperature above 100 degrees Celsius.

As the outer joint, and based upon your experiment, is in direct contact with the hot water there is a good chance it will disengage with the pipe upon expansion.

And I would expect the glue that was used was probably a water based glue as an epoxy glue cannot re-plasticize after first application (or it was poorly glued in the first place).

Originally Posted by Loy Toy

As the outer joint, and based upon your experiment, is in direct contact with the hot water there is a good chance it will disengage with the pipe upon expansion.

Ahh yes, good point. The heat is being applied from the inside when in use

Originally Posted by Loy Toy

And I would expect the glue that was used was probably a water based glue as an epoxy glue cannot re-plasticize after first application (or it was poorly glued in the first place).

The standard PVC solvent had been used.
He was doing an emergency repair at night and need to re-use the fittings

A bit off-topic but I need advice here.

I have had more than my fair share of trouble when installing PVC ball valves.
The solvent just doesn't seem to work on the ball valves as well as it does on the fittings.

errmm, where would you use solvent on ball valves?

they are screw fit, as far as I know, you just screw on the pipe fitting and use the white tape

then the pipe can be glued into the fitting

This type of ball valve
It is glued in

Originally Posted by Thetyim

The solvent just doesn't seem to work on the ball valves as well as it does on the fittings.

Solvent based adhesives and most crystalline structure plastics don't go well together due to the fact the solvent migrates into the plastic structure melting/ softening/ eventually destroying it.

Keep the solvent well away from the ball joints and apply sparingly where you need it.

Other than that you can heat weld or use a clamp to secure the joint with silicon as your major sealant.

great thread and useful for me. our builders tried to install the green hot pipe themselves without "the tool" by shaving and fitting the pipes together with Thai Pipe. they leaked at every joint as soon as we tested - even with cold water. if you use green pipe you have to get that tool. its porous otherwise.

we ripped all the green pipe out and have open walls on the outside of our house. my wife called the pipe company and they said blue pipe is rated to 80C. since our boiler wont go over 40C i think it will work. now i am just waiting for all this rain to stop so i can get it done myself.

i only had a question about the heat rating of Thai Pipe glue. anybody know this one?

i thought about just wrapping the joints with heat tape after i glue the inside and outside. but maybe its not required.

Originally Posted by Thetyim

This type of ball valve
It is glued in

aha!! that type, sorry, I assumed you were referring to the floating ball valves for water tanks etc (ballcocks)

as for these, I have had no problems using the normal solvents

not sure why you have

Originally Posted by pkspirate

my wife called the pipe company and they said blue pipe is rated to 80C. since our boiler wont go over 40C i think it will work. now i am just waiting for all this rain to stop so i can get it done myself. i only had a question about the heat rating of Thai Pipe glue. anybody know this one?

I think that was discussed already; the pipes are Ok for reasonably hot water but the joints are the weakest link

should be OK for you though at 40C

Originally Posted by DrAndy

I have had no problems using the normal solvents

OK, thanks
Maybe I will have more luck if I try another brand.
I spend extra time preparing the surfaces to be glued and leave double the time for the glue to set but some of them just fail