Looking online, the k1 is cheaper than the k7, any substantive reason to choose the K7? I am having a hard time determining the differences between the k7.1,.2,.3, but read about issues with one of the k7 unloaders.
Any advice would be appreciated. Think my unloader is going, have a backup but need a backup for that one once replaced.
Get the K7 if you like having to fiddle with unloaders during jobs. Otherwise the K1 is fine.
Thank you sir. I donāt like messing with anything, at all. I just want to put chems in my tank, fire up the rig, and start spraying and praying. The k1 is about 1/2 price vs the k7 at the PW store I normally order from.
Get the K1 be done with it. Mine has been darn near perfect since I put it in early last year. It did have a slight ācavitationā feel last month but a little tweak on the adjuster bolt cleared it up.
Thanks. Appreciate the feedback.
I donāt see your gpm but I will say the ZK1 wouldnāt work with my 4 gpm rig last year when I tried it. At 6.8 it has enhanced my quality of life around the clock to say the least.
Thank you for taking the time to respond. Guess the zk1 will get ordered this weekend.
If you donāt have an extra one on hand get one ordered ASAP. Thatās a tell tell sign itās on itās way out
No kidding! Iāve got 500ish hours on mine & today it decided it didnāt want to do any surface cleaning. Just pulsed on and off, same with a pressure nozzle. Worked great until then. Going to get a fresh one on the way & attempt to see if I can get this thing apart to have a gander. The Pulsar got me through the job but the Dirty Harry recoil has got to GO.
Keep worn spray nozzles on hand to squeeze more life out of it.
Have you had one of these things apart? Iām a bit curious if it has a wear component where the failure occurs but have zero clue of the mystical inner workings. I just thought it was magic or something until today.
The orifice enlarges. I use a .1 size (ZK5.1) even though I was flowing 4.75 gpm. And the spring gets weak.
You know your stuff dude! Sharp as a tack.
My knowledge base is only a reflection of my years here on earth 
Sadly I started my journey late in life conquering CAD, CAM and CNC. Mechatronics will be where it ends. Iām turning 47 the 20th and Iām nowhere near where I want to be! Spent way too long behind a gun I suppose.
had a fiasco today replacing my old trapped pressure unloader with the zk1. What a nightmare. The old stuff was plumbed using 1/2". I couldnāt find parts to replumb. Finally found parts about 30 minutes away, but I had to fab with reducers and bushings to get it how it needed to be. The old one stood higher, and had big 90ās off it going up. From the factory, leak free for at least 4 years, maybe 4.5. Redid it and it was like a sprinkler system. Used tape, used paste, cranked on it, Dissassembled, reassembled. yadda yadda.
Turns out the one fitting had a little cut in the end of it. Went back to the store and bought 2 more after examining them. What a huge PITA.
The zk1 has less reach and pressure than the old one, kinda miss the distance already and I was just testing it in the yard. But as @dcbrock says, no more bird nesting, what a relief. That gets so old.
Why did I wait so long you ask, when I had one as my backup unloader on the truck?? I donāt like messing with stuff that is working just fine. Call me stuck in a rut, or old, or cheap, just has never worked out for me when I tinker with something to improve it. Just worried all my wood nozzles on their jrods are not going to be sufficient anymore. I think it will work fine for vinyl.
Moral of the long winded story: check your fittings before you leave the shop/store. I had screwed some stuff together in the store, but never checked the opposite end. Have a breaker bar handy for wrenches, make sure it is wide enough for all your tools. And I have the backup zk1 on the trailer already, cheaper at the kentucky store than the ohio k7.
/end rant-therapy session
Huh? What pressures were you running before? You need to do some more adjusting. All Iāve run for several years on 3 different machines and they all basically output pump specs
One manās .02. I literally was using the old one the day before for about 3 hours of mostly gun time (gen 1 trex deck with lots of lichen), with a little vinyl section to be washed. After I put this on I immediately noticed a difference in the pressure and the range/reach. I didnāt put a gauge on it, but Iāve been using that BCE trapped pressure unloader for years (it does sit unused for about 6 months a year due to winter). I adjusted the zk1 unloader like the good people here taught me years ago, until there is a trickle coming out while on the gun, then lock it down. Is there something I am doing wrong with that? The only other logical reason is that the zk1 is 3/8 and my old one was 1/2", so maybe this restricts flow more. Maybe using the zk1 I donāt need a trickle coming out while on the gun?
Love to know the reason, thinking I lost maybe 4-5 feet of range vertically, where it matters most. I tested it on my house, couldnāt reach sections I could before. Iām more than ready to be corrected on how to adjust the zk1, you can yell at me too if I am doing it wrong. I want those feet back.
It was over power level 9000!!! Just playing, that is an old Japanese anime meme
I donāt believe the ātrickleā rule applies to flow sensitive unloaders. I have not noticed any difference between pressure/flow unloaders in terms of distance/spray pattern over the course of 4, 5.5, and 8 gpm pumps.
1/2 to 3/8 might be the difference maker, but Iām not sure.
I just read the manual that they never send with the units. Here it is
Choose the correct nozzle size, able to discharge regularly, on bypass, at least 5% of the total flow of the system in order to achieve a constant pressure, and avoid troublesome pressure spikes.
Prior to start-up set the ZK1 unloader to it lowest pressure setting by turning the adjusting screw (item 12) clockwise until stop and make sure the system has an adequate water supply.
Follow pressure washer manufacturerās safety guidelines for start-up and start the washer.
Once running, cycle trigger gun open and closed four or five times to purge any remaining air and to make sure the ZK1 unloader is functioning properly.
With the trigger gun open (spray mode) gradually increase the pressure by turning the adjusting screw (item 12) counter-clockwise, increasing pressure by increments no greater then 200 psi cycling the gun at each interval. If at any point the unloader does not unload properly, return the pressure to minimum and repeat adjusting sequence.
Once the system is brought up to rated pressure cycle the trigger gun four or five times to make sure it is functioning properly and set the jam nut (item 13).
Shut down the washer and restart and confirm the pressure setting.
Reading this makes me think they are suggesting a trickle (well 5%). I guess I could measure that to make sure, but then I have to disconnect the unloader hose and get a bucket. Then math makes me think that if it was 7.5 gpm, I should have about 1/3 a gallon in a minute. But then I think that was the old readings with the old unloader, so maybe I get less flow now. Looks like I have more adjustments to do no matter what.
https://www.powerwashstore.com/Content/files/PDFs/GP-ZK1-Unloader.pdf
That is the link I used for the info, if anyone else wants it.
