A Checklist for Winning Solar Thermal Value

Price is what you pay – Value is what you get.

I have my own story about glycol pumps which I’d like to share with all of you guys.  We'll call it "The Big Bang" - or - "When Things Go Wrong on the Job"

As a 21 years young apprentice working for Walter Zimmerly -one of the best HVAC contractors I ever met (Augsburg, Germany), I was in charge of picking up materials and tools for my crew and other crews and getting the items to the job sites the following morning.  I would typically receive a list at the end of the workday - after the various crews had already headed home.

One list contained a surprising item: “die SPUELMASCHINE” – if you translate the word to English – a Dishwasher! I looked all over the shelves and cabinets of our shop storage for a dishwasher and couldn’t find it! Finally, I worked it out; - hey we need a machine for glycol, so I need to look for a pump!

Needle in a Hay Stack

There were threading machines, drain cleaning machines, hammer drills, work benches, boiler dolly, drum truck, 4-wheel truck with piped boiler, big plastic box on a 4-wheel truck with a power cord attached…,   but only one thing seemed to match the request – small plastic drill pump with a “Praktiker” name on it, with attached hoses, one of them sticking in the drum of glycol.  I took it.

Next day our first job was a vacuum tubes replacement, damaged by the hail on a 360-tubes system, 80 clicks away from our shop. We left the shop early, got there at 7AM.

We Raised our ladders, dropped the pressure, drained the manifolds on the roof, got broken tubes down, and installed new ones. 9:30 AM. “Let's pressurize the system before the sun cooks it”, - said Thomas, my foreman, -“Where is die SPUELMASCHINE?”

And now I’m coming back from the truck with that “Praktiker” tool and corded drill in my hands. By our foreman’s facial expression I knew what I was going to hear next.. But instead he just looked on his watch and asked me what I want for lunch!? Nice guy! He is leaving to get die SPUELMASCHINE and I suppose to wait. And he was gone.

I felt that I had screwed up something and as a fix, I decided to get the job done alone, and when Thomas comes back, we will have our lunch together and everything will be OK after that.

Well, after connecting all hoses to the pump and pipes I pushed the drill trigger – its running! After a couple minutes I realized that there is no flow at all. I needed to prime the suction hose! After ten minutes I finally got the flow moving!

Looking on the depleting glycol in the first pail I’m now thinking how I will switch the hose? Too late! - the pump sucks in air.  Ten minutes later… The pump is hot, but I can’t stop here, the loop has to be filled and flow restored, or the system will steam! And I pushed and pushed the trigger!

I will never forget what happened next: The drill consolidate texas payday loans in my hand began vibrating and then just went on high RPMs.. almost simultaneously the vinyl hose attached to return pipe became a bubble!

Scared - I shut all the drain valves off. And before I realized what had happened – loud bang noise and whole boiler room filled with the steam, stinky glycol steam!

… The BIG BANG live experience.

That big plastic box I saw in the shop, on a 4-wheel truck with a power cord attached, was die SPUELMASCHINE, - the Handmade Solar Filling station with submersible high head sewage pump, temperature resistant washing machine hoses rolled together and kept inside the big plastic container.

Who could possibly know that?

Lucky me; - neither I was hurt in that accident, nor I was fired by my boss. But I learned many lessons from the experience.

A Proper Solution

A few years later first industrial-made, professional filling stations for solar thermal trades’ people became available and it was from ZUWA Company . They got it right.  And if you my friends, are looking for a pump as A TOOL which wouldn’t let you down in any circumstances, you need say YES to all of following questions:

  1. Is the pump self priming?
    Dry running the pump will kill every pump. Positive displacement pumps with flexible impeller have high suction; you will empty your pails with them.
  2. Does it have adequate flow and head characteristics?
    A high flow rate is a main feature of a good pump as it mainly influences the performance when it comes to remove air trapped in the collectors. A powerful pump also speeds up the charging process, saves time and your money.
  3. Is the working liquid temperature high enough?
    Permissible media temperature should be at least 60°C /140°F. All startups and most service work are completed in conditions with warm or hot Glycol. This characteristic should be the same for pump and hoses.
  4. Is there Easy access to the filter?
    The particle filter should be easily accessible for cleaning – not only after the job is done but also during work. The ideal solution is a filter in transparent container. This way you can see it before is too late.
  5. Can that pump work with other liquids?
    The robust flexible impeller design makes the pump suitable for the transfer of fluids with a wide viscosity range, pumping water, diesel, glycol, heating and engine oils.
  6. Can the pump be drained easily?
    And if you pump different liquids, it is important that only a minimum quantity or nothing of it remains inside the pump after the job is done. In a simple garden pump with an injector, up to half a gallon of glycol may remain in the pump body. Impeller pumps are draining completely. The pump should also drain the container completely. It is a time consuming process to manually drain the pump prior to each change of media. Remainders can also leak out during transport and make a mess in your tool box or truck.


Yes! -is the answer for ZUWA UNISTAR pumps.
And after comparing all your answers for tool you use now it should be easy to decide for the right tool – get a ZUWA. It’s as simple as that!