Serious cold water rig problem...plz help!

[Aqua Pro 22]

Its so nice to have a "goto" guy in this industry. I love the Grime Scene Forum...my "goto" NETWORK! ;-)

My cold water rig is mounted in an inclosed trailer and has a 15 gallon float tank attatched to it. It is a 13hp, 4gm, 4,000 psi Blackknight belt drive unit.

Originally, I had the float tank on the floor next to the machine and everything worked great. No issues with pressure or draw.

Last year, the machine started cavatating and my pressure greatly dropped. At first I thought it was an unloader issue and that is the first thing I looked at. I made sure there was no debris inside of it and then eventually changed it completely.

That did not fix the problem so then I took a look at the pump itself. I took off all the valve covers and visually inspected it. Then took it one step further and just replaced the valves themselves "just in case". That too did not fix the problem.

The only way I could back to full pressure is by running the water directly into the pump thereby forcing water into it. That gave me full pressure back.

I ran it like that for the remainder of the year and just allowed my float tank to overflow via the bypass and flooded my trailer everytime because A) I was fed up with messing with it and B) Was busy.

Anyway, I thought the beginning of my new season would be a good time to fix this issue. Since I have already looked at the unloader and valves and CAN correct the problem by forcing water into the pump I next concluded that it must be the fact that the float tank outlet is lower than the pump inlet so I raised my float tank to be above the inlet and hooked it up back the right way. Guess the news....I have lost my pressure again ;-(

Remember, it used to work great when first rigged up..now the only way I can get full pressure is when attatched directly to the pump inlet. It seems like the pump is not drawing water from the tank like it should. It seems like it is just taking whatever "flows into it". PS- When I remove the hose from the float tank off the input side of the pump, the water flows very good at "free fall." so nothing is blocking the hose.

What gives? Anyone have an idea?

[big mike 14]

My first instinct is to check all the fittings and look for an air leak. If that's all good, make sure your supply hose isn't collapsing from the suction (common problem). Also, if your supply tank has a lid on it, that needs to be removed, or a vacuum will be created and restrict water flow to the pump.

[Chris Tharpe 40]

Change out your inlet hose to spa flex (white thick hose at Home depot or Lowes) and then go from there if that doesn't fix the problem. I am guessing your getting some sort of air leak as well, try moving the inlet hose around and see if your problem stops while your moving it.

[Russ Johnson 141]

How old is the machine? Could be your inlet seals are getting tired, and are allowing a bit of air suction.

[Aqua Pro 22]

Thanks for the replies and for the phone call (you know who you are ;)

I changed the hose from the tank to the pump, reapplied teflon, checked for air leaks as best I could.....same problem. Extremely low pressure and cavatating... run garden hose directly in and wah-la awesome pressure again.

Mind you this is only a 12-14 inch section of reinforced heater hose and is higher than the inlet...if I disconnect the hose from the inlet and let gravity take over it would appear that it runs very smooth.

The only thing I have not tried is removing the tank lid, however two points about that 1) It worked before with the lid on and 2) the tank has a vent hole on top. It's still worth a shot but im almost positive that I have run the machine with the lid off already with no improvements.

Around 34oo psi with direct water and 500-600 using float tank. ..hose is not collapsing either.

VERY frustrating!! grrr!

[Scott Stone 604]

I am with Russ. The seals are shot. Really, they are a wear item. Just plan on it, they are not that hard to do, unless you are Gene...

[Edward 14]

I would go with the seals also. Most pump manufactures offer pump seal kits that give you all you need to do the job.

Good luck

Ed