New Pump Seal Failure on Start-up

[0ralph]

Hello,

I am trying to rebuild a 1999-ish Jacuzzi spa. It has 2 pumps.

The old J-pump (jet pump) did not come on, so I removed it and took it to a pump repair shop. The inside of the motor was completely corroded to the point that I had to buy a new pump. (I was later able to determine the gate valve positioned directly over the J-pump was leaking which is most likely what caused the corrosion in the old pump.)

I opted to replace it with a more generic 1.5 HP Waterway pump and plumb in new gate valves and new pump unions to match it, instead of purchasing a new Jacuzzi J-pump (6x the cost). After I had all of this installed and turned on power to the spa, the older Jacuzzi recirc pump comes on without any issues. Water is coming out of all the jets. When I go to turn on the jet pump, the seal immediately pops and water starts gushing out of the back of the wet end.

I assumed this must have been a defective seal, pump, wet end, whatever and I was able to RMA it for a replacement.

The second pump did the exact same thing. Seal immediately blown on start-up.

Instead of trying to RMA it a second time, I elected to purchase a new wet end and install it myself, potentially ruling out the possibility that someone at the factory is not installing the wet ends correctly.

The exact same failure a third time.

At this point, I am at a total loss for what is causing this problem. There has to be something I am doing incorrectly! I have absolutely no idea what would cause these brand new pumps to fail within seconds of being turned on.

Does anyone have any idea what might be causing this?

 

[Texas Splash]

Welcome to TFP! Any chance you can post some pics of your set-up? I'll also tag @RDspaguy to see if he notices anything odd in your description.

 

[RDspaguy]

Ok. A J-pump is a type of wet-end, not a "jet pump". They have been discontinued, but an aftermarket replacement is available, though the parts don't swap out. And it is pricey!
I can't say that I've ever had this problem, but here's what I know.
-On those older jacuzzi spas both pumps push into opposite ends of a common, shared plumbing system. This creates pressures in the system much greater than either pump by itself. It may be that your combined pressure exceeds the pressure rating of the pump/ seal in the new pump, so blows out the weak point. Is your new pump a higher HP or flow rate than the old one? I seem to recall those being one hp, but it's been many years. Increasing pressures on these is a bad idea, and can cause all kinds of problems. Are all of the jets open?
-There is usually a check valve to prevent backflow through the pumps, but the location can vary, and may or may not play a part in this. But a broken check valve can close a line just as start-up pressures reach their max, causing compression and the resulting kickback, which I've seen blow apart valves and unions. It could blow a seal as well I would think, if nothing else gave out first. Do you hear a distinct "thump" right before it blows the seal?
-You might also try a better seal if it's not any of the above. Get a "supreme", which has a metal casing over the rubber diagphram of the seal.

 

[0ralph]

Here is a picture of the label from the old pump I had to replace. I no longer have the pump, I wish I had taken more pictures of it.

 

[0ralph]

These are the old Jacuzzi-style unions and leaky gate valves.

And the new unions / gate valves after I replaced everything.

 

[0ralph]

@RDspaguy

I would concur with everything you stated. I think it is a little strange the way this thing is plumbed. There is a check valve on the outlet side of the smaller pump. I had to replace this check valve as it was glued to a leaky gate valve (I had to replace all the gate valves).

It looks to me by following the pipes like the smaller pump might actually be able to push water through the larger pump backwards if the larger pump isn't running. I am not an expert in fluid dynamics, but this obviously worked fine with the Jacuzzi pump for almost 20 years, so I'm not sure that the plumbing design is really the problem here.

The replacement pump is actually a 1.5HP. Notice the old Jacuzzi pump doesn't even have an explicit HP rating, the label just has dashes next to HP. I'm not necessarily trying to increase the pressure on this system, though.

After the 3rd round of blowing the seal, the company I ordered the pump from elected to send me another new pump, free of charge (totally unexpected, all I was doing was asking them for advice). However, they didn't have any more 1.5HP pumps in stock with 2" fittings, so they sent me a 3HP pump. (You can see where this is going...)

After 3 failures and not having any idea why it's happening, I decided to film the whole process of installing this 3rd pump for my 4th attempt and turning it on. I uploaded an unlisted YT video here so you can see it: link.

The video will give you views of the smaller pump and the new plumbing I installed.

After reading your post, and thinking about this just a little, I'm curious if maybe the wires for the 2 pumps are backwards? The one with the check valve is the one that turns on automatically just to bring up the temperature and run on the programmed schedule. Maybe it's supposed to be the other pump? I'm not sure.

Thanks for all your help!

 

[RDspaguy]

The pump in your pic connected to the heater is pump 1, which runs for filtration and heating.
The old pump is 240v 5.7 amps. What is the new pump?
I don't see a check valve in the pics. Is there one still, and is it facing the right way? Is it broken? It only takes one hit with too much pressure to break it.
I'll watch your video in a little while, bedtime for the kids...

 

[0ralph]

This is the inlet and outlet of what is connected as pump 1. I have replaced these gate valves and the check valve. The new ones can be seen in the video.
After I read your first post, it got me thinking there is not actually a need for this check valve on the outlet here because it wouldn't be possible for this pump to be off at the same time the other one is running unless the pump itself had already failed. UNLESS, this is actually supposed to be pump 2.

I think they have been hooked up backwards this whole time. I think it's even plausible that the previous owner switched the plugs when pump 1 failed thinking "oh, well it works this way."

I will take pictures of the labels of all the pumps tomorrow morning and post them.

Again, thanks for your help.

 

[0ralph]

Labels from the still-working older pump, and the new pump.

 

[RDspaguy]

this is actually supposed to be pump 2.

Yes.
I don't see any issue with the pump hp.
(Watched video. It was slightly painful, but with a little practice and some training we'll make a tech out of you in no time. Nice catch on the loose spade terminal.)
WTF?!!! That thing blew up! And it's pump 1, so no check valve until pump 2. Are the jets open? Each jet nozzle screws in and out, open is out.
3hp is WAY too much, but the 1.5 is only a bit over. I'm guessing the original was 1hp. I can't imagine why this would happen with the 1.5, unless the fact that water is flowing backward through it at start-up plays a part. Can't say I've ever reversed pump connections on one of these. Switch the pump plugs so that the one on the right of the controls that is plumbed directly to the heater is pump 1, and make sure all jets are open.
Take the 1.5hp pump wet-end apart and post pics. I'd like to see exactly what happened. If it broke the impeller or ruptured the seal.

 

[RDspaguy]

There's a reason they don't plumb them this way anymore, and I think we're learning why. The more I think the more it makes sense. Kinda like putting your car in drive while still rolling backwards. I'm betting the impeller is snapped off the shaft.

 

[0ralph]

All jets were wide open. I had done some testing with a vacuum to check for blockages, which was one of the things I thought might cause this. I'm Sorry if the video was painful for you to watch. I can only imagine a seasoned tech would loathe witnessing all of the silly things a newbie would do. But I wanted a chance for someone else to see what I was doing in hopes they could figure it out. I, however, have no intention of becoming a spa/pool technician. I just like the challenge of fixing old things.

I do have a shorter video of me tearing down the 1.5HP pump after the last seal blowout (before the 3HP incident). It's only 5 min: link. The company I purchased the pump from suspected the shaft was bent on the pump, so they wanted to see it turn. That's what got me started making these videos. There you can see the impeller. Strangely enough, there doesn't appear to be any noticeable damage to the volute or the impeller. I have a few of these wet ends laying around now, so this one in the video is the one I will attempt to repair. I've ordered a new seal and impeller. (I took your advice and ordered the "supreme" seal just in case.) I can't tell if the impeller is damaged or not. There are metal shavings present inside the threads which might suggest it is stripped out. They aren't that expensive so I am going to replace it.

I have not torn down the 3HP pump yet, but if you want to see it I'll post some pics tomorrow. There is almost a perfect cutout in the exact same size/shape as the slinger/wear ring/whatever-you-are-supposed-to-call-that-thing right in the face of the wet end. Almost like the impeller unthreaded itself and pushed out against the outlet. It happened quick though -- you saw it in the video. We're talking a fraction of a second.

It will be next week before I get all the parts. Hope I get to make some progress putting this back together.

I definitely owe you a tip, a case of beer or whatever bribes you accept.

 

[RDspaguy]

Pay it forward. That's what I'm doing. You can thank the guys on a diesel truck forum for my being on this forum.
I really though that impeller would be broken off. In 26 years at this there have been a handful of head-scratchers that I never did figure out what or why, even if I fixed them in the end. This is one of the darndest things I've seen. It has to be related to the pumps being in the wrong plug. You could dead-head that pump (close the output valve) and it would not do that, so it must be due to having flow backward through the pump at start-up. Nothing else makes sense.
Keep us posted, I'm very curious to know if that takes care of it.

 

[0ralph]

Even if this works out well, I am expecting the control system to fail at some point (20-year-old electronics). It looks like it might be possible to cap off the intake into pump 2, then tee off the outlet of pump 1 back into where pump 2's outlet is and then replace the entire spa pack with a single 2-speed pump control system. Does that seem like a reasonable modification to you? I'm asking because even if it is reasonable, there might be implications I'm not thinking of! Thanks.

 

[RDspaguy]

It's a balboa, which is the brand I'd recommend to put in it anyway, and will be an easy swap. I've put many balboa packs in old J-pump tubs. You can set up a new balboa vs system to operate almost exactly as this one does or with a 2-speed pump. You might even be able to make that one run a single 2-speed.
Many of those older Jacuzzi tubs with digital electronics were a single 2-speed pump. The 2 single speed pumps are a hold-over from their older non-digital controls.
I would not leave ANY pipe stagnant. Don't cap, plumb it all in. Suction to suction, with a ball valve or spring check valve for filter flow control, and pressure to pressure.