Locating a leak in high pressure water plastic plumbing

[DaveC426913]

My hottub has a leak in its high pressure plastic plumbing. I've replaced what parts I can but am having trouble locating the leak since I have to drain the tub completely to examine it.

Can anyone suggest a dye or something that will allow me to locate the leak even after the water is drained? It needs to be something that will not gum up the parts or permanently stain the tub lining.

I tried a mixture of food dye but it is not very effective because
1] the water must be many gallons to fill the system, thus it is dilute
2] the dye escapes and mixes easily, obscuring exactly where it's coming from

 

[brewnog]

Dunno how big your system is, but some of the dye they use to trace underground waterways will do the job. Wonder what it's called; if you find out let me know!

 

[DaveC426913]

Well, it's just a hottub. The plumbing itself holds maybe 20 gallons; the tub, about 300.

Problem with dyes is that they'll stain the tub.

I suppose one other thing I can do is raise the whole kit & kaboodle up so I can get under it and see the drip. I'm not relishing crawling under something that weighs a ton or more. Or building a truss that'd hold it.

 

[Danger]

Can you be more specific about the plumbing set-up? For instance, are all of the pipes easily observable, as opposed to buried? Do you at have at least a suspicion of where it might be, so you can check there first? Not meaning to sound facetious here; it just seems that you should be able to see where it's coming out if everything is in the open (without having to crawl under it, I mean--won't a good flashlight give you enough vision?)
I can see that being difficult if everything is wet all the time anyhow. In that case, I'd consider drying everything off, painting on a thin layer of something like liquid latex, and then watching for a balloon to form. If overall wetness is caused by condensation, that should be on the outside of the latex, not the inside. Depending upon the set-up, you should be able to blow-dry it from outside and use a spray wand for application. Then you don't have to worry about the tub falling on you.

 

[DaveC426913]

It's a soft-side tub. The superstructure of the tub IS the plumbing (1 1/2" ABS) with vinyl draped over it. I can pull the vinyl off (partway) and see OK, it's just that the leak is tough to identify. It will be on the very bottom. The leak was caused by freezing.

 

[brewnog]

The dye I mentioned won't stain, unline crack-detection penetrant dye etc.

Danger's idea of the bubbliness could work; try washing up liquid too.

 

[DaveC426913]

Well, the trouble I'm having is the difficulty of examining any of the piping without completely draining the tub of water so I can pull the lining out. This is why a "real-time" detection method is problematic. I've been looking for a method that leaves evidence AFTER the water is drained.

But Danger's brilliant idea of simply "looking" (no, I'm not being sarcastic) has inspired me to try looking with the water still in it, as I think I can get at it without disassembling and inverting the whole thing.

 

[brewnog]

Ahh I see.

If you suspect it to be the tub itself, you could fill it up, wait for it to leak, and the level at which it ends up is the level at the bottom of the crack.

 

[Echo 6 Sierra]

From Brewnog: try washing up liquid too.

Yes, good idea. If you have a small spray bottle mix some liquid soap with some water and spray in suspected places then watch for bubbles.

 

[Averagesupernova]

First thing to do is consider which fittings and pipes are most likely damaged by frost.

 

[Stevedye56]

Are the joints glued together or are they screwed in with teflon tape? If its not to hard to drain you could take it apart and inspect each seal. Maybe an o-ring or a gasket is damaged.

 

[DaveC426913]

Ahh I see.

If you suspect it to be the tub itself, you could fill it up, wait for it to leak, and the level at which it ends up is the level at the bottom of the crack.

The water empties until it reaches the lowest inlet. This is how I know it's in the plumbing, not a leak in the lining.

Um. See pic. A computer model is worth a thousand words...(couldn't resist)

Are the joints glued together or are they screwed in with teflon tape?

Glued. And boy that that ever make replacing sections a pain. See, you can't just cut anywhere, you have to "back up" until you have room to add a joiner. To replace the adapters around the pump required me to "back up" so much I replaced about 4 feet of pipe and about 8 joints - twice!

I am in the midst of checking all threaded joints, adding plumber's tape and replacing any o-rings.

 

[Moonbear]

From Brewnog: try washing up liquid too.

Yes, good idea. If you have a small spray bottle mix some liquid soap with some water and spray in suspected places then watch for bubbles.

You can do this with the tub drained if you have an air compressor to blow air into the pipes (assuming you can blow air in without further rupturing pipes)...wherever water leaks out, the air will bubble up the detergent solution too.

 

[Cybersteve]

I suspect the most likely location of a leak is where the pipes pass through or are connected to the lining.
Can you prop up one side of the tub?
This would immediately tell you which side the leak was on and repeating the process would narrow your search further.

 

[DaveC426913]

I suspect the most likely location of a leak is where the pipes pass through or are connected to the lining.
Can you prop up one side of the tub?
This would immediately tell you which side the leak was on and repeating the process would narrow your search further.

That's a clever idea!

 

[Danger]

There might be a simpler way. Can you replace the water with sardine oil and drop a cat nearby?

 

[DaveC426913]

Tried it. Cat simply jumped in tub, drowned in its own ecstacy.



Here's what the spa guy suggested:
Turn it on.
Step 1: Plug the intake ports with my hands
If the leak is on the suction side of the system, it will draw air. If it doesn't, it's not in the suction side of the system.
Step 2: Close all the jets (I forgot you can do this). Water will jet out the leak at high pressure.

It seems obvious in retrospect. The thing that was fouling my logic was the problem of how to fill the tub with water while still being able to pull the lining away to get at the plumbing without all the water pouring out. Being able to turn off the jets and plug the intake ports facilitates this.

 

[brewnog]

Sorry, I'd not realized it was a nice squirty bubbly air system!

Glad you're sorted.

 

[Danger]

Tried it. Cat simply jumped in tub, drowned in its own ecstacy.

Nuts! I should have foreseen that.

Your spa guy sounds pretty savvy. Sign him up for PF.

 

[Ivan Seeking]

Here's what the spa guy suggested:

Hee hee. You came to PF before calling the spa people?

 

[Stevedye56]

Oh now i see, i was under the impression that it was just the water in pipe. Now i see my suggestion would be ridclious because you would have to almost completely take apart the hot tub.