Hydros flow sensor threads leaking

[Florida_fish]

I feel silly but wanted advice before I take everything apart. Brand new build. I have a 1" Hydros flow sensor plumbed into my return line. I used the supplied schedule 80 unions. The threaded side seemed to screw all the way on to the sensor without the usual PVC thread tightness on the later threads. I used liquid teflon pipe sealant. I've used the same sealant on other PVC threads on the build and they aren't leaking, but I've got a pretty dramatic drip from both sides of the sensor from the threads. I thought about just wrapping teflon tape on the threads pretty thick to get better friction but I'm not sure that will work either. Any advice would be greatly appreciated. thanks very much.

 

[JeffB418]

Reach out to [email protected] and they may have some good suggestions on ways to correct this issue.

 

[pookie]

I am having the exact same issue! New tank new fluid sensor and leaking out both sides on both of my sensors

 

[BeanAnimal]

I feel silly but wanted advice before I take everything apart. Brand new build. I have a 1" Hydros flow sensor plumbed into my return line. I used the supplied schedule 80 unions. The threaded side seemed to screw all the way on to the sensor without the usual PVC thread tightness on the later threads. I used liquid teflon pipe sealant. I've used the same sealant on other PVC threads on the build and they aren't leaking, but I've got a pretty dramatic drip from both sides of the sensor from the threads. I thought about just wrapping teflon tape on the threads pretty thick to get better friction but I'm not sure that will work either. Any advice would be greatly appreciated. thanks very much.

Those sensor ports are likely BSPP straight threads, which are not sealing threads.

If the union half threading onto the sensor doesn’t have a gasket or washer interface (think garden hose), then the threads themselves aren’t going to seal. That’s why it runs all the way in and still leaks, there is no taper or gasket.

You can sometimes get parallel threads it to seal with a combination of tape and paste, but you will likely need RTV silicone on the threads.

I wouldn’t put it past CV having no clue on how parallel threads are supposed to seal. They are not engineers. The union that they provide should have the proper washer or or dowdy seal, but I would bet they don’t.

 

[UncommonSense]

likely BSPP

This is… concerning.

 

[BeanAnimal]

This is… concerning.

More common than you would think, straight threads BSPP (Europe and Asia) and NPS (US) are common on industrial sensors and fittings and instrumentation. The issue is not the threads, but rather the vendor not providing or understanding the proper termination.

Straight threads are used so the threads only hold the parts together and a gasket or washer makes the seal. This gives predictable sealing torque and avoids the stress that tapered threads create when they wedge together.

 

[UncommonSense]

The issue is not the threads, but rather the vendor not providing or understanding the proper termination.

My thoughts exactly!

It’s a problem normally associated with products sourced from the cheapest possible vendors… it’s concerning to see that CV made that business decision…

Comically bad, one might say.

(I’ve also seen true FNPT fittings which were made a touch too large, causing every MNPT part you try to seal in to leak… same root cause, though… [the only bulkhead fittings BRS currently sells, for example…])

 

[pookie]

So I found a solution sort of... so yes as stated above when you thread this thing on all the way you can look inside and see that there are 2-3 threads inside that cant thread on because of the housing for sensor... I cut the union in half with a dremel on the side that goes onto the sensor and used plumbers tape and problem solved magically doesnt leak anymore... not sure how this could slip past quality control... im going to call them tomorrow and tell them and needing a replacement for one fitting as its too damaged as I glue the other part in already......

 

[BeanAnimal]

Read above. is not a quality control issue. It is the way the threads are designed. The issue is CV Hydros not providing the proper union because they don’t understand what they are buying and reselling.