Good article on CFM, Waterlift.

This is a very informative article about the debate over cfm and waterlift:

http://www.hydramaster.com/inside/articles/articles2.asp

It's interesting to notice that truckmounts have lifts in the 13-15" Hg range, which is equivalent to around 175"-225" waterlifts, yet at cfm's around 300-500 or so. 

So when you consider running a portable with vacuums in a series, say 2-3 stage vacs, you will get upwards of 220" of waterlift, but the cfm will drop down to 90 or so.

When you run vacs in parallel, the waterlift will be around 140", which is around 10" Hg, but the cfm will then be at 200.

It would appear that running these vacuums in parallel would closer mimic the balance of cfm and waterlift that truckmounts use, but of course scaled back to portable levels.  When vacs are run in a series, the lift is as high as truckmounts, but the cfm is proportionately far lower, thus throwing the balance off.

As the article pointed to, only recently have more become aware of this balance.  Of course there have obviously been some who have been pioneering this understanding for many years, but the great majority haven't been listening, including your's truly I must admit.


Edited by Johnsmith808 - 23/December/2007 at 5:22pm

Wonder where they learned that??????????? (!!!!)


merry Christmas;
Ed Valentine
cross-american corp.

Buy something F A S T and make some loot..!

I just got an explanation of where vacs in series or parallel would be beneficial.  I'm sure you guys already know this, but please be patient.

I was told that vacs in a series would be better with low pile, commercial type carpet.  I would think that would be because the seal is pretty good at the wand, so lift would come more into play.

Vacs in parallel would better suite thicker, residential carpet, due to the seal not being as tight, thus airflow being better.

Does that sound about right?

Johnsmith808 wrote: I just got an explanation of where vacs in series or parallel would be beneficial.  I'm sure you guys already know this, but please be patient. I was told that vacs in a series would be better with low pile, commercial type carpet.  I would think that would be because the seal is pretty good at the wand, so lift would come more into play. Vacs in parallel would better suite thicker, residential carpet, due to the seal not being as tight, thus airflow being better. Does that sound about right?

Perhaps, but if you've ever seen that carpet, I would think you would wonder what the difference is. That pile is so thin that "pile" is almost an oxymoron. Sure the seal is strong, but how much water can you get in 1/8 of an inch of carpet?

Thanks Friendly.  I think I'm going to go ahead and turn my machine into parallel vacs.  I'm also going to make the intake on the recovery tank 2" instead of 1.5.  Shouldn't be too hard.  Of course I would then need to run 2" hose.

Yesterday I did a job using 15 feet of hose, and it dried faster than any job I've done recently.  It was actually easier to work with 15 feet of hose than 25 feet for the most part as well.

The only reason I use 50 feet sometimes is so I don't have to carry the machine upstairs on a two story house.  Now I plan on getting a continuous piece of 50 feet 2" hose and running the machine in parallel.   And for one story units, I'll stick with the 1.5 inch 15 foot house.  Would 2" on such a short hose even matter?

Add it.. I did on my Recoil.. Faster dry times..