3/8th vs. 1/2

[Jeff 232]

I had a guy from TCN contact me. He just bought a Pressure Pro 8GPM machine and he's having pressure problems. He said that with 150' ft of 3/8th pressure hose he loses pressure down toabout 2900psi, he was asking me and i told him i havent notice a problem with mine

He was told by pressure pro thats its because he is suppose to be using 1/2 pressure line. Iwas told 3/8th is just fine, is that true about the 1/2 inch line. What does everybody use with their 8gpm

[PWkid 79]

Jeff I run a 9.3 gpm and a 8.5. I use 3/8 hose and haven't had noticeable problems. I know rule of thumb is 100 psi per 100 ft of hose. On my hot water set-up if I run water through my coil I lose a few more hundred psi because of the around 200 ft of coil its going through so I put quick connects on each inlet and outlet and run a jumper so I can bypass my coil when not using Hot Water.

[Mike Williamson 198]

I had a guy from TCN contact me. He just bought a Pressure Pro 8GPM machine and he's having pressure problems. He said that with 150' ft of 3/8th pressure hose he loses pressure down toabout 2900psi, he was asking me and i told him i havent notice a problem with mine

He was told by pressure pro thats its because he is suppose to be using 1/2 pressure line. Iwas told 3/8th is just fine, is that true about the 1/2 inch line. What does everybody use with their 8gpm

Is he getting 3500psi at the pump? You WILL get more pressure drop with 3/8 than you will with 1/2, but I've not had any problems with mine running 3/8. Then again, I haven't checked the pressure at the end of the hose. It works fine, so I've not felt the need to check.

[jbruno 14]

It doesn't matter the gpm rating , what's the psi rating. If he's got a 3500psi machine and he's down to 2900 it may be the problems Mel and Mike spoke about. Also, he should check his tip size he has while running the machine.

[Mike Sullivan 15]

When I switched from using a 4gpm pump to a 5.5gpm, I had pressure drop problems too. I discovered my unloader was the problem. You will have to screw it down tighter for larger gpm machines to compensate.

Mike

[sarowe 14]

Recently had pressure drop problems also. Check the obvious like the tips and unloader adjustment but my problem turned out to be a bad unloader. Check recent 'pump pressure' thread because the guys helped me a lot with the troubleshooting.

[VanDiesel99 14]

3/8 will create a pressure drop in high flow machines. Question is whether the psi drop is worth dragging a larger/more expensive hose around to compensate for. Plus using guns with oversized oriface so the gun doesn't restrict the flow. Plus do 3/8 fittings restrict it? If so you will have to find 1/2" QC's. I got a 8gpm Hydrotek and I bought specific nozzles for my surface cleaner to match up with the max pressure for the flow. When I tried it they didn't spin very fast because the flow was being restricted. I simply bought smaller oriface surfacer nozzles and eliminated the problem. The psi/flow drop is not that much.

[Beth n Rod 1,279]

3/8" lines limit your chem injectors ability over longer runs. 50' is about max before it loses ability to pull chem.

1/2" lines allow better flow throught the longer runs to allow the injector to still function.

Rod!~

[One Tough Pressure 580]

Pressure drop on a 3/8" hose at 100 feet on a 5 gpm machine is 130 psi. The drop on that same hose with an 8 gpm is 300 psi. So with 150 feet of 3/8" hose on an 8pm washer, you can expect a 450 psi drop.

That drop is from hose alone and does not count the unloader, coil, hose reel and so on.

[Mike Williamson 198]

3/8 will create a pressure drop in high flow machines. Question is whether the psi drop is worth dragging a larger/more expensive hose around to compensate for. Plus using guns with oversized oriface so the gun doesn't restrict the flow. Plus do 3/8 fittings restrict it? If so you will have to find 1/2" QC's. I got a 8gpm Hydrotek and I bought specific nozzles for my surface cleaner to match up with the max pressure for the flow. When I tried it they didn't spin very fast because the flow was being restricted. I simply bought smaller oriface surfacer nozzles and eliminated the problem. The psi/flow drop is not that much.

It isn't that the 3/8 hose and fittings are too small for the higher volume machines, it is that the water loses pressure due to friction with the hose. The smaller the hose, the larger percentage of the water flowing through the hose is creating friction with the walls of the hose. Larger hose, less percentage of water making contact with the hose, and less friction loss. Unless you're talking some mammoth machine much larger than an 8gpm, I don't see that you'd need to do anything except increase your hose size, if you couldn't live with the pressure drop. For 90% of my work, I'm running low pressure anyway, so using a larger hose would be pointless. For the concrete cleaning, I can live with the pressure drop. I just can't imagine pulling 200+ feet of 1/2" hose. I don't even like using 2-wire 3/8 hose!

[Jeff 232]

Thank you all!! I'll pass this on

[VanDiesel99 14]

Yea I have noticed the chem injector also doesn't work with the 3/8in like Rod said.

[PWkid 79]

3/8" lines limit your chem injectors ability over longer runs. 50' is about max before it loses ability to pull chem.

1/2" lines allow better flow throught the longer runs to allow the injector to still function.

Rod!~

Rod that is not a true statement.I pull chem on both of my machines with 300 ft of hose everyday.

[Beth n Rod 1,279]

Rod that is not a true statement.I pull chem on both of my machines with 300 ft of hose everyday.

This is based upon actual experience Mel. I was using a 3gpm 2700psi machine and it would not draw through the new 3/8 line I replaced the OEM lines with. I even installed a new injector first but after talking with the manufacturer and trouble shooting, they discovered the replacement line I bought was the problem. I changed the line to a 1/2 line and the injector functioned.

While this may not apply to ALL injectors, it still is a factor to be considered in the topic.

Thanks for sharing your experience. Just for the record, can you also post your machines gpm/psi for others to consider? This may be a factor.

Rod!~

[PWkid 79]

Rod I appologize, I read my post and it sounded to me like I was being a smart arse. I wasn't I was just saying that with the right equipment you can pull chemical farther than what manufacturers tell people. When I responded to Jeff I relayed my gpm which once again is 9.3 @ 8.5 gpm. I also in another thread I mentioned that with a smaller injector than what the machines gpm is rated for you can pull chemical farther.

[VanDiesel99 14]

Doesn't using this undersized downstreamer create backpressure on the pump and pressure or flow drop? I tried the big orifaced downstreamers and the smaller ones and I couldn't get it to draw hardly any chems.

[PWkid 79]

All chem injectors create back pressure I would think so anyway. When you try to push water through a tiny hole thats what creates the venturi effect.I notice flow drop but not too much pressure drop. Michael I am not sure why your machine isn't drawing chems all I know is that I use a 3-5 gpm injector for my machines and it draws chem through 300 ft of hose. I am not a physics major but I do have experience I can tell you what works but not why. lol There are some very smart people on here they might be able to explain it.

[Chappy 138]

I just got an 8gpm skid. there are times Ive had to pull 400 ft of hose around. I may get some pressure drop but Ill be darned if im going to pull that much extra weight around with using the half inch.

ive never been able to get draw from my chem injector with more than 100 ft of hose with my old 5.6gpm skid. now that Ive got the bigger unit, maybe the same 3-5gpm injector will draw with longer hose lengths.

[Mike Williamson 198]

Rod that is not a true statement.I pull chem on both of my machines with 300 ft of hose everyday.

I pull plenty of chems with an 8gpm machine and 200' of hose. I haven't tried longer runs with this injector, but it works much better than the last one I had, so it may well work with longer hose too. I also am using the 3-5 injector rather than the 5-8, and it works great!

[Mike Williamson 198]

All chem injectors create back pressure I would think so anyway.

Yep, that's why they work. I imagine that if you use TOO small an injector with too large a machine, you'll be creating too much back pressure and will engage the unloader, but that's not the case when I use the 3-5 injector with the 8gpm machine. Works like a charm.

[PWkid 79]

Actually Mike on my 8.5 gpm cold water I use a 2-3 gpm and it pulls a lot more chem when I need it. It was an experiment that worked out very well. I checked my head pressure with a gauge and while I was injecting it read 3000 psi. It really sucked the chem lol no pun intended.

[VanDiesel99 14]

So do you pull the injector off when you start washing?

[Mike Williamson 198]

So do you pull the injector off when you start washing?

You mean when I start rinsing? Nope, I just put in a 2520 tip (for an 8gpm machine) and start rinsing. The injector only works at lower pressures.

[PWkid 79]

If I am cleaning concrete I will pull it off.

[Grime Dawg 14]

Spoke with Bob from Pressure Tek recently about this same downsizing of the injector trick. According to him it only works with machines 5 gpm or higher.

If you've got a smaller gpm machine, it may pay to give him a call to verify before investing in another injector.

Todd