Ok so when mine was leaking it was coming from here where the blue arrow is. It was presumably from a bad o-ring or gunk in the o-ring
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to access or look at the o-ring which is a very unique design, almost like an H with 2 o-rings connected. I had to move this little clip here and push the valve out ward. It was a bit tricky to do but it can be done. I think this is what
D
deeda
is telling you to do?.. when you open this up you may be able to look at the o-ring to see if it is broken or just has some funk in it, needing to be wiped off.
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Hopefully this is helpful. One more thing I would add in conjunction with what deeda was explaining, keep in mind when you are opening up your hoses that they will have a syphon that you will need to break by taking out the intake or return. You may already know this, but if not, hopefully I saved you from a small flood. Not going to tell you how I found this out ?