K7 Vs ZK1 unloader or anything better?

Was reading through the master blaster truck build post and saw some talk about K7 and ZK1 being two good unloaders. Are these the two best ones on the market or are there other ones that may be more expensive that might be superior in someway? When I bought Hydrotek‘s most expensive machine it said it came with a K7 but when I went to go get it serviced at Hotsy Mechanic told me that I had this little cheapy one on there. I’m going to be honest, I know very little about unloaders. My mechanic told me that my psi is going down from its initial output because the unloader is starting to wear out. He tried to turn it up as much as possible while monitoring the Spike Pressure and I cannot get any higher than 2600 psi now. I was at 2800 with the 200’ of hose. Price is not a concern as I want the best performance and best reliability. I have a 7.8 GPM 3000 psi machine. I also downstream at 250’ sometimes. Currently Soap is not a problem at all and I am using the 5-8gpm orfice in my DSI.

I have both and prefer the ZK1. K7 was far more finicky to set. ZK1 was not finicky at all and easy to set.

ZK1 has the soft start feature too right? My guess is this one is probably the best one to use out of anything else on the market? Here’s another one I found that’s $189 which is pretty expensive. I don’t know what would make this one cost so much more. The only thing I can see is it says that it relieves all the pressure in the entire system while on bypass. Is that standard? https://www.toolbarn.com/giant-8-712-705-0.html/?gclid=Cj0KCQjwufn8BRCwARIsAKzP6963xnSLM9FjSIe5eCdF_ivFsGEHIwoS-WhcEwOgb6iVpi_pg4CbETsaArA8EALw_wcB

My Hydromax comes with a K7 I believe and i asked them to put a ZK1 on there instead. No blowback when you squeeze the trigger, no orifices to mess with, doesnt care what size bypass hose you put on either. Go with a ZK1.


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$72 kleenrite

linked it above

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Did you use QC for your unloader or mount straight on the block?

This is the only guy I’ve seen with an expensive unloader, that he claims to do better than the K7s. I have had K7s and now the ZK1, and I do like the ZK1 better as well. No reason for me to change, running an 8 gpm.



Straight in the block but QC into almost everything else.

My machine is powered by Kubota Diesel. There is no option to idle down so it seems the one benefit doesn’t apply to my setup. My current unloader is a VRT3 which I guess is a really cheap one. After spraying for even 30 minutes ( on off the trigger ) the heavy 2 wire hose will kick itself back 10-20’. I wonder if the zk1 would prevent that from happening? And if it does maybe I could once and a while only unreel what I need instead of all 200’ and use it without fear of birdsnesting and getting it all bunched up on the reel?

He had me interested till he said $275 for an unloader. The K7 last me forever but they are a pain sometimes.

I’m not sure I understand where idling down matters? It’s just a flow actuated unloader, which results in no kickback when you pull your trigger.

That’s an excellent question, would the ZK1 allow that? I get so tired of unrolling all 200’ for every job.

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I don’t have to unroll if I don’t want to. No hose jumping for me.


I got the top of the line machine with worst unloader lol. That’s like getting a new multi zone furnace with an analog controller. Ordering ZK1 tomorrow!

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I run a K7 with a #2 orifice and 3/8 bypass on my Kubota, it doesn’t matter if I’m at fun throttle or idle, it’s fine. #3 orifice would cycle a little at idle, but not now with the smaller orifice. I just idle a little too warm up and go operating RPM, but the bypass works ask the time.

@Seandz I would trust a 6 year old to squeeze the trigger on my machine with a k7… Without a doubt

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So, when you press the trigger, the hose doesn’t stiffen and expand on the reel? Trying to picture how it doesn’t birdsnest, if that’s the case I’m ordering a zk1 tomorrow.

Can you repost the link? It doesn’t work. Thanks man.

You can get anywhere. Don’t be lazy, go to KLeen-rites site and search