Leaking union

[Amanda1234]

I have a hotspot spa and the one union is leaking.  We have replaced the oring and tried a gasket even though it did not have one originally.  We have tried hand tightening and a little more then hand tight.  It is still leaking.  It is spraying out the top, not a small drip.  
If it sits without pressure there is no leak, but the moment the keys come on it sprays.  
Any suggestions on a fix as I am stumped.  
 

the original o ring had a small bit of wear on it when replaced.  
 

I attached photos of the union and original oring. 
 

also is there any way to test without filling and draining the tub each time??

[CanadianSpaTech]

13 hours ago, Amanda1234 said:

We have tried hand tightening and a little more then hand tight.

Is there ant tension on the hose when trying to align it with the pump and will it sit flush against the pump. Sometimes there can be a bit of tension and the oring won't sit flush. It can be flush on one side and 1/8" out on the other. I use an oil filter wrench/pliers to tighten. You can also use a flat head screwdriver and place it against the nubs the go around the coupler then gently tap it with a hammer to get it tighter. 1/4 turn can make all the difference

 

13 hours ago, Amanda1234 said:

also is there any way to test without filling and draining the tub each time?

No

[Cusser]

If mine, I'd make sure there was no crack there, and try a new thicker O-ring.  And maybe use some pool silicone grease on it, maybe even some automotive RTV or Permatex Aviation.

The O-ring has to compress to seal. 

This reminds me of my old 1984 Jeep Cherokee, the mechanical fuel pump leaked oil where it bolted to the engine.  I got a new gasket for it from the parts store, noticed that the O-ring seemed too thin to compress, and of course that leaked oil too.  Sine the fuel pump was lifetime warranty, and I figured maybe its flange was warped, I exchanged it for a brand new one; guess what: the new fuel pump came with a thicker/different design O-ring and that never leaked.

To get additional torque for tightening, I use a ViseGrip 12LC or a rubber strap wrench.  You're not tightening to the point of breaking anything however, just to compress the O-ring some.

 

[Amanda1234]

We did tighten with screw driver and hammer.  I do notice that when we move the pipe coming out of the heater it has movement, like threaded piece sits tight, but the pipe moves side to side.  No other connector in the tub does that.  So not tight enough?   I don’t want to crank on it and it crack.  There are no cracks in the plastic.  
It seems like it’s not level or the oring is not sitting level like you mention so when pressure is applied it leaks.  
many suggestions on leveling?  Or do we replace the plastic ring with the two nut type?  We pay for water so this is driving me nuts filling and emptying 

[RDspaguy]

Better pics! What am I seeing there, water shooting out of the union toward the hose or water from the hose? Is that a crack in the first elbow? 

Check the union flange for cracks.

[CanadianSpaTech]

4 hours ago, RDspaguy said:

Is that a crack in the first elbow? 

good eye

[Amanda1234]

It is not cracked.  That’s a surface scratch from removing tape when we tried to stop the leak over the winter.  
 

there are no cracks in the pipes or the fittings.  The water sprays out the top of the union when pressure is applied, at the threaded joint. 
 

we picked up oil filter wrench and tightened with that and there is no movement now.  Just waiting for the weather to cooperate so we can fill the tub again and test.