Radiant Heat Problem

My underfloor radaint heat has worked great for years , all of the sudden it's taking a long...........time for my radiant loop of my house to come up to temp. Can it be my taco 5000 mixing valve. it is set for 135 and it is maintaining that temp no problem . So I have a feeling it's my mixing valve can anyone help with the problem.
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On Dec 17, 8:45pm, smc22_at_mac_dot snipped-for-privacy@foo.com (smc22) wrote:

Maybe pump is worn out, maybe valve, maybe air in lines, maybe get a pro its something else.
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