Yes, it technically could be used, however it would violate electrical code, and the ground clamps used for piping that size are extremely expensive. A ground clamp for 1/2" up to 1" pipe is about 5$. When you jump to 1 1/4" ground clamp the price jumps to about 50$ each.
Also, some meters like the Fluke T5-1000 only measure resistance up to the 1000 ohm range.
Relying only on a breaker and not a GFCI to protect you in case of a ground fault is plain stupid, and what we in the electrical trade would call natural selection. If there is an electrical fault to ground, the breaker may not trip (for a handful of reasons) and still create a shock hazard. Use the GFCI and don't disconnect the ground. By tripping, it is doing it's job.
You said their is a ground lug on the GFCI... What brand/model is it? I've connected quite a few GFCI's and never seen one with a ground terminal; usually only 2 hots and a neutral. However even if this is the case, it probably wont fix your problem.
Replace the element, don't risk your life with electricity.
Also, some meters like the Fluke T5-1000 only measure resistance up to the 1000 ohm range.
Relying only on a breaker and not a GFCI to protect you in case of a ground fault is plain stupid, and what we in the electrical trade would call natural selection. If there is an electrical fault to ground, the breaker may not trip (for a handful of reasons) and still create a shock hazard. Use the GFCI and don't disconnect the ground. By tripping, it is doing it's job.
You said their is a ground lug on the GFCI... What brand/model is it? I've connected quite a few GFCI's and never seen one with a ground terminal; usually only 2 hots and a neutral. However even if this is the case, it probably wont fix your problem.
Replace the element, don't risk your life with electricity.