How I got started on Loop

So a week ago Friday I decided to start with LOOP. I just followed the directions at It was a bit intimidating at times because all the involved systems are so big and unfamiliar, but I just followed the instructions step-by-step and the result was working software on my iPhone. The hardest part actually was signing up for the Apple developer account: somehow an essential button wasn’t appearing on the web page for me, so I was stuck until the button finally showed up after a few reloads of the page. And then the several-hour wait for the approval email from Apple.

I started the software open loop running to my old 723, which had firmware 2.4A. Unfortunately, I had forgotten that my old 723 was replaced under warranty because of some kind of hardware error, and the one I actually have is firmware 2.5A. It works fine in open loop, but the pump won’t accept any commands related to dosing insulin. (They took those commands out to protect us from the hackers who might surreptitiously give us fatal overdoses by radio.) When I first put the battery into the 723 it rebooted itself twice in the first 5 minutes because of internal errors, but after that it settled down and seems to be working properly.

In open loop I enjoyed seeing the loop’s prediction curve showing what it expected my CGM graph to look like in the future, and seeing the curve change over time as reality failed to match the expectations (typically because of my underdosing for meals.) The prediction graphs did cause me to be less aggressive in corrections because of the predictions that my rising trend would get better all by itself starting in 20 or 30 minutes if I just wait. I worked through multi-hour moderate highs when the suggested corrections were not enough, but I’m spending much less time low — my worst problem. It worked better when I found the bolus tool (the double down triangles in the middle at the bottom of the screen. To me, this is the “I want more insulin” button. It suggests a correction bolus that really does help, and acts as a conservative sugar surfing wizard while keeping me away from rage boluses.

I was able to get an ancient 515 demonstrator model from my endo’s office. It got an A21 error right away, then rebooted. A21 might mean a failure of the internal battery that keeps the pump running while you switch the AAA cell. After rebooting it seemed ok, so I entered my settings, put in a filled reservoir and tried to prime. The plunger moved to the reservoir at high speed, and then kept right on on going, spraying a hundred units of insulin out of the tube before giving an A33 error. That error might mean failure of the sensor that detects back pressure on the plunger: the pump never knew that it had contacted a filled cartridge. But the pump didn’t brick itself. After rebooting and many many rewind/prime attempts, I finally got the screen saying 0.0 primed which means it did sense a filled reservoir. By then there were only 60u left in the reservoir, but I decided to run closed loop with it.

LOOP is outstanding. Far away from meals it keeps me more or less in a flatline with no attention from me at all. And I’ve been making my carb ratio and correction sensitivity more aggressive, which is helping LOOP get a good response after eating.

It’s clear that LOOP was designed for the convenience and comfort of the pump user, not the pump manufacturer’s legal staff. It is wonderful to be able to get a meal bolus with a minimal number of keystrokes; the (user-adjustable) safety guardrails in the software are quite thoughtfully designed to protect against blunders without being intrusive.

After the initial 60u ran out I went through the same ordeal with the next reservoir. Multiple A33 errors and reboots. By the time the pump would let me stop priming there was only 12u left. This is not sustainable.

After the 12u ran out, I decided to prime against the eraser-end of a pencil rather than against a reservoir filled with insulin. It took a half hour, but I managed to get out of priming mode with the plunger at about the 160u mark. So I filled a reservoir to 160, screwed it into the pump which pressed out just a few drops of insulin, and have continued looping. Quite a nuisance, but LOOP is so wonderful that it’s worth it, and I’ll keep doing it this way until I break the pump because it doesn’t know to stop the motor when there’s too much backpressure. (This also probably means it can’t detect occlusions, but I’ve only had one in the last 5 years.)

Any tips on finding another pump? I found nothing suitable the past couple days on craigslist or ebay. MedWow shows some expensive pumps that might work if they are not scams, but the LOOP documentation at says “Medwow has been fairly frustrating for most people; poor response rate, high prices” and then goes on to describe all the ways we can get scammed when web-ordering a used pump from a random posting. So that makes me extra wary.


@bkh congratulations for setting up and starting Loop. I managed to find a pump by setting up an “insulin pump” alert on craiglist, in which I included locations within reasonable driving distance. When a post showed up, I quickly replied to the poster, and arranged for a meeting to inspect the pump, which turned out to be a 522 in great shape. But, this was some time ago, and I know it’s becoming increasingly difficult to find a suitable pump these days. Wish you best luck and success.

Thanks for the tip. I had looked on craigs list a few times without finding anything usable, but today I looked and someone had posted a 722 just two hours earlier, and it was only 3 hours away so I was able to go, see that it boots up and primes without fault, and bring it home. I’m really really happy now. Such exquisite good luck.


Wow, that’s great! Fortune favors the bold, happy Looping!

Sounds like I should be rushing out to sell my old MiniMed pumps. I might be able to make quite a profit! I’ll have to look up the models when I get home today.


Make sure you check the firmware version as well. If the pumps have been upgraded too much, they are not helpful.


It’s been a while since I’ve checked. How much are these selling for these days when you’re able to find one?

going rate is $300 - $500, for honest brokers at least

On MedWow the 722 generally runs $800 to $1200, mostly $1000 with a few outliers. There are some indications that these are models that some flipper has snatched off of places like craigslist and then marked up for resale.

The 722 I got was $500, direct from a type 1 that I met in person. He wanted to be sure that it was going to someone who could use it, rather than to some reseller business. The 722 was his backup pump, and he was about to get a new pump and didn’t need two generations of backups.

Is the 722 the most desired model?

515, 715, 522 or 722 are all fine. For 523. 723, 554, or 754 you’d need to check firmware version. Here is a complete list of compatible pumps and CGM systems.


Thanks for posting this. I think I have the 715 and 722, but I might have the 723. That one is also bright pink, so that may influence the price :wink:

If both meet the criteria, I’ll probably sell one and keep the other in case I change my mind and want to go back. Makes more sense than having two pumps lying around that people really want to use.

1 Like

yes, the word on the street is the MedWow is a pretty sketchy and frustrating place to get a pump. Craigslist or local diabetes support groups are much better.

1 Like

I think it depends on your needs. The 723 has a higher minimum basal rate, so we have it as a backup for openAPS but ideally wouldn’t have to use it.

1 Like

I prefer the 7xx over the 5xx because of the larger reservoir (don’t have to fill as often). In terms of reliability/longevity, the x15 are oldest, the x22 are newer than that, and the x23 are even more recent. I’m guessing that an older pump is more likely to fail.

Consider starting looping on one and keep a second as a backup. I’ll post before and after graphs when I’ve got a few more days data on the loop, but I can already see that my control is much better now that I have software pushing my BG in the right direction every 5 minutes. I had good A1C before, but now I have no lows and much milder high excursions. On top of that, there’s the beneficial change from “I sure am glad my CGM wakes me when I’m going low at night” which now has turned simply to “Zzzzzz.”

1 Like

On the other hand, the x23 has finer dosing increments (at least than the x15 models.) And on the 515 it seems that the insulin:carb ratio is whole numbers only, so I can’t choose 1:5.2 I have to choose 1:5 or 1:6. That’s not as big a problem as it might seem at first glance, because LOOP will set temp basals to correct the drift from a basal that’s not quite right.


I’m sure looping is incredibly beneficial for basal rates. I’m really not a fan of having something attached to me all the time though. The Dexcom is small enough and beneficial enough that I put up with it. I think I’d only go back to a pump if MDI was no longer working. Even then, I’d probably want to try a tubeless pump.

Maybe I should just sell both of my pumps… haha

I’m glad it works so well for you!

1 Like

I’m holding out for the drivers to be worked out for the Omnipod. I just don’t know how I could prevent my 6 year old to not rip out a tubed pump. He pretty much wrestles with his brother every day.


Our friends run a jui jistu club. They have two Type 1’s that don’t have problems with sites getting ripped out. It is possible.

1 Like

My kids are basically feral when they play together and Samson’s site usually is pulled out about once every month or two. But usually not by his brother. So it can be done – especially if your son is able to articulate when his pump site gets ripped out; it’s a minor inconvenience but the fact is we have to change out his sites sometimes sooner than anticipated for any number of reasons.