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Asphalt Sealcoating System Tip: Losing Pressure at the Spray Tip

Have you suddenly lost pressure at the spray tip of your sealcoating machine? There are a few different reasons why this can happen.

Reason 1: Sealer Dilution

Losing Pressure at the Sealcoating Spray Tip? Photo by Beth Kingery (flickr)
The first reason could be that the sealer is too thick:  it is not diluted enough with water. Sealer is sold as a concentrate, therefore all sealer must be diluted with 20 to 30% water dilution.  That means for every 100 gallons of concentrate, you need to add 20 to 30 gallons worth of water.

We always recommend that you add the water to the spray system tank prior to transferring sealer concentrate over to the tank. Mixing it thoroughly and making sure your sealer is diluted will allow you to have a sealer that is at a dilution level that can be sprayed with a spray system.

If you’re applying the sealer by hand with a squeegee or sealer brush dilution is not as necessary because it can be applied in a viscous state.

Reason 2: Blockage in the Sprayer

Sealcoating sprayer pipe blockedThe second reason why a sealer spray system may not be spraying is because the unit may have blockage down at the main suction pipe. The suction pipe connects to the very bottom of the tank and runs to the suction port of the pump.

If there is sediment at the bottom of the tank that was built up and blocking or damming that main suction port on the tank, then the sealer would be just trying to suck from a dead end.

So, it’s very important that you either purchase one of our manual agitation kits and manually mix the tank prior to turning your unit on, or you take a rebar or some kind of a paddle or mixer that you can get in through the top lid and move the sealer around down at the bottom of the tank where the suction port is.

Reason 3: Clogged Spray Gun

Clogged sealcoat sprayer can be another cause of poor pressure at the spray tipThe third reason that you might not have proper pressure at the tip is in the case that you have a trigger spray gun. Over time, if it’s not cleaned and flushed at the end of every day, it will get backed up and blocked up in the handle. You’ll be at a job site and your system will spray fine for a minute and a half or so, and eventually pressure will build up and back up towards the pump and the pump will lose its prime.

To prevent this from happening, it’s important to clean out that trigger gun every couple of days, or every day if you can, just by removing it and flushing fresh water through it and moving that trigger handle around.

Those are the most common reasons for losing pressure at the spray tip.


There are a variety of ways to troubleshoot these different issues.

  1. If your sealer is too thick: Determine if this is the problem by adding the proper water dilution. If you haven’t calculated it and you’re going just by guesstimate, what we recommend that you do is you put your transfer kit on your unit, have that transfer kit put into a 55-gallon drum of water, turn your unit on spray mode and start your unit up. That will bypass your main tank, sucking from your transfer kit out through your spray gun spraying with water. If you have proper pressure there during this water test, it means that your sealer is just too thick. Keeping track of your sealer dilution is very important.
  2. Blockage: If you are concerned about whether your pump is working or not and wonder if there is some kind of blockage down at the bottom of your tank where the suction port is attached, what you can do is put the transfer kit on, bypass your tank, and spray out of your spray gun. If when you are sucking from the transfer kit out your spray gun you have proper pressure, then you know that the problem is in your tank.The whole key is to figure out whether there’s a problem at the tank or at the pump level, and the way you do that is by bypassing your tank through the transfer kit.
  3. Trigger gun: The easiest way to know if the gun is the problem is to always have a ball valve-style spray gun handy. If the system works well with the ball valve-style spray gun you know that the trigger gun is blocked.If you don’t have a ball valve-style spray gun you can always disconnect the hose from your trigger gun and just put that spray hose, holding it carefully in the top of your tank (so it doesn’t spray all over), and see if you have good pressure coming out of that hose without the trigger gun.

If you are losing pressure at the tip and you still need to finish a job, then you could always have your squeegee or sealer brush with you as back-up. Simply take your hose off of your spray gun, whether it’s ball valve or trigger, and pump sealer out onto the driveway. Spread it with a squeegee or sealer brush as a worst-case back-up scenario so that you can finish the job and keep your customers happy, and then do your troubleshooting back at your shop.

Those are a few tips on how to resolve issues if you don’t have proper pressure at your tip. Questions?  Feel free to post them below!

2 thoughts on “Asphalt Sealcoating System Tip: Losing Pressure at the Spray Tip”

  • Eliza Cranston
    Eliza Cranston December 22 at 10:37 am

    This was a really helpful guide to seal coating problems! I have an asphalt driveway and I'd like to put a seal coat on it before the snows set in this year. I've had some problems with the sprayer so I'll investigate all of these possibilities and see if I can get it working again. How would you recommend clearing a blockage in the tank?

  • Gina Henrie

    I have noticed a little bit of lost pressure at the spray tip of the sealcoating machine my husband has. I never thought that it might be because the sealer is too thick. I don't think he has thought about that either, so I will ask him and have him take a double look at it.

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