Submersible Pumps and multiple check valves?

[Cacher_Chick]

In the June issue of "Well Driller" magazine, there was an article that discusses the proper use of multiple check valves in a well. Having heard Speedbump's reasoning for using NO check valves in the well, I'm left quite curious as to what standard practice is in the industry.

The article can be viewed at http://www.nationaldriller.com/Articles/Column/BNP_GUID_9-5-2006_A_10000000000000350695

 

[Valveman]

Bob Pelican writes some very good stuff. However, on the issue of check valves, he has taken the engineers view, which is not a practical stand point. As long as all the check valves are new and working perfectly, you can get away with using multiple check valves. There are only two kinds of valves in existence, those that leak and those that will leak. The minute one of them starts dragging or leaking, which they will, many problems arise.

This is just one of those things that works on paper, and not so good in reality. A check valve is designed to stop water from going backwards. You don't want water to go backwards when the pump shuts off, so if one check valve is a good thing, then a hundred check valves should be better.

However, the more check valves you have the more friction loss you have. A bigger pump is needed if you have much friction loss. Other than that, you would still think an extra check valve or two would still be a good idea for backup.

Many times, multiple check valves do work OK when everything is new and working perfectly. The problem comes when any check valve leaks a little bit, or doesn't close quite as fast as the check valve above it. Then a negative pressure is created below the top check valve.

If the top check valve is above ground, the vacuum can draw contaminates into the line. No matter if the top check valve is above ground or in the drop pipe, the negative pressure will allow the pump to start to the right of it's curve. (In other words "wide open") The pressure above the pump will change from negative pressure to positive pressure in a fraction of a second. The effect is, the column of water below the top check will "punch" the top check. This is much like a Boxer "punching" you in the face. It creates a shock wave that travels throughout the water lines. At every outlet valve, elbow, tee, and dead end in the pipe, the shock wave turns into water hammer. Water hammer causes everything in the pipe system to experience pressure 10 times what you see on the gauge. On larger pumps it usually causes the pressure switch to bounce on and off like a telegraph.

You can remove the upper check valve when they start causing problems, or you can install only one check valve at the pump and not have the problems.

I have installed systems as deep as 2200' with only one check valve. You just need a good check valve, and to start and stop the pump at "almost" deadhead pressure conditions.

The only check valve you should have on a submersible pump system is the one on the pump itself. Another check valve anywhere else can cause a vacuum or negative pressure before the second check valve. If that second check valve is above ground, the potential of drawing in contaminates because of the vacuum conditions is probable. If the second check valve is below the pitless, on anywhere on the drop pipe, the potential of a water hammer event happening at each pump start is very real.

Using a second check valve just in case the one on the pump fails is never a good idea. If the check on the pump fails, it must be replaced. Having a second check valve will only mask the problem of the first check valve, and cause water hammer and possible contamination in the process.
Cycling the pump on and off is what destroys check valves and most other equipment in a pump system. The check valve slamming shut from a full open position when the pump is cycling repeatedly is the main cause of check valve failure. Using a Cycle Stop Valve on your pump system dramatically reduces the number of times your pump cycles, which will increase the life of the check valve and all other components in the system. The Cycle Stop Valve is also in the 1 GPM position, not fully open, when the pump shuts off. This means that the check valve is also only open to 1 GPM, which is only the width of a piece of paper, not fully open, when the pump shuts off. This means that the few times that the Cycle Stop Valve allows the pump to cycle, the check valve does a nice gentle close, which eliminates water hammer and check valve failure.

Multiple check valves work good on paper but, cause multiple problems in the real world.

 

[Sponsor]

 

[99k]

Valveman
Thanks for the very interesting and informative commentary. In our area, I have never seen a system without a check valve inside the house at the cross of the pressure tank. Are you saying you don't recommend installing those either? My experience has been that many of the check valves with new submersible pumps, such as two name brands, cannot hold a column of water right out of the box. It has been explained to me that the quality of these valves is very low in order to reduce costs. That would become a very expensive repair to pull a pump if it's the only check valve. Comments please.

 

[Speedbump]

In my experience, the check valves that come built into or screwed into new pumps are of decent quality. As a matter of fact, the only one I remember going bad was in a Sta Rite pump back in the eighties. They had a hard rubber gromet that did the actual seating and it would break off causing the valve to hammer when the pump turned off. I have seen many of the add on brass valves go bad, mostly because of the springs either breaking or coming detached from the valve. Another problem was the retaining stem breaking due to rattling around in it's holder wearing the brass thin enough for the poppett to actually break free and head upstream to a fitting it couldn't get through. At this point the check valve was working in reverse and stopping or hindering water flow upstream.

Another problem with leaking back was with the Myers Rustler sub not too many years ago. The plastic discharge head of the pump would split letting water run back which would cycle the pump to death. The check valve worked fine.

99K, I'm not sure what brands you are referring to since you probably pulled them out of the post for liability reasons. I would be interested in what brands they are. You could PM me and share the news. These brands may not even be available in my area, so I wouldn't be aware of any check valve problems with these select pumps.

The plumbing inspector in my county made it code that every new well installed since the 90's has to have a check valve at the well head. This does not make it a good idea. I for one don't like to see one anywhere except on the top of a submersible pump. The only exception would be with a galvanized tank with an air making system installed.

bob...

 

[Valveman]

Some states like Nebraska require an additional check valve at the pressure tank. Other states like Michigan are smart enough to completely outlaw any additional check valve above ground. If I lived in Nebraska, I would wait for the inspector to leave, then I would remove the check valve at the pressure tank. I don't care if it is state law, I would not want to take the chance of the check valve causing contamination and water hammer to MY water system.

Yes, many of the pump manufacturers use very cheap check valves in there pump heads. Others like Grundfos, Unitra, Hydroflo have an excellent check valve built into their pump heads. These check valves actually work better if they handle the entire load by themselves. You do need to start with a good check valve at the pump. However, even cheap check valves can easily handle the weight of the water column. They just won't last long if you let them slam shut from the full open position, which causes 10 times more pressure than normal pressure and height. No matter how many extra check valves you have, if the one on the pump fails, it must still be fixed.

Reducing the flow from the pump to 1 GPM before the pump shuts off, as a Cycle Stop Valve will do, eliminates the slamming of check valves, stops water hammer, and makes the check valve and everything else last longer. The CSV also starts the pump against an almost closed valve, which eliminates the check valve poppet flying up on start up.

Some variable speed systems such as the Franklin Sub Drive and Mono Drive are actually harder on check valves than a regular system with a tank that is cycling rapidly. This is because these Franklin systems use a switch instead of a transducer. The switch will make and brake 45 times per minute or 2,000,000 times per month. This causes the pump to ramp up and down 2,000,000 times per month, which also causes the check valve to open and close 2,000,000 times per month. None of the components can last very long doing this 2,000,000 times per month. It is just luck if the switch, bladder tank, motor, or any of the other components down in the well out last the check valve.

To answer your question, NO, I do not recommend more than one check valve on any water pump system, unless it is used as part of the air make up system with a galv, tank.

 

[99k]

Thanks Valveman. It's interesting how installations vary geographically.

 

[Gary Slusser]

Only one check valve in or on the outlet of a submersible pump. I've not pulled near as many pumps as some but I've only pulled two pumps that had a broken internal check valve. I've replaced many at the pressure tank that were broken and I think it was because they are installed horizontally.

 

[Valveman]

The check valve at the tank breaks often because it receives a "punch in the face" from the water hammer when the pump starts, caused by having two check valves.

 

[hickster]

check valves

Wisconsin also outlaws check valves installed above ground. In my neck of the woods we always place one an inch or two above the pump and that's it. Everyone does this, and have for quite some time. I never see problems with this application, except maybe when iron or other mineral deposits are present and than no one wins . no hammer etc. I have seen the valves at the pumps leak by periodically. Any feedback?

 

[Speedbump]

We practically never have problems with check valves on pumps. The ones that come with the pump that is. These above ground valves that our moron plumbing inspector decided would be a good thing and added it to the code is a problem though. There is no argueing with him though. I tried that route.

Wisconsin has long been ahead of most states with good Water Well Practices. I applaud them for that. Michigan usually adapts Wisconsin code and their practices are pretty sound as well. Florida... well that's another story.

bob...

 

[Valveman]

Don't get me started because Texas officials are still living in the dark ages. Anyway, I don't usually have problems with the internal check valve either. At least the ones that are made like Grundfos, Hydroflo, Unitra. The little plastic ones with the bar across the top to keep the poppet from coming out are pretty bad though.

However, even a cheap check valve will last fine if you don't let it slam or the pump to cycle excessively. When used with a CSV, the pump is only pumping 1 GPM when it shuts off. At 1 GPM the check valve is barely open the thickness of a piece of paper, so you don't get a slam when it closes. And it doesn't even do that very often.

With a standard pressure tank system, the pump is delivering max flow when it shuts off, and the pump will cycle a lot. That means that the check valve is slamming closed from the full open position, and it does it numerous times per day. That is what destroys most check valves and multiple check valves just make it worse.

 

[Gary Slusser]

I get 2-3 emails per day concerning any news about water quality etc. from a company that is notified when something newsworthy happens. WI has been having some serious contamination problems with wells in some large areas of the state. For years a government employee there in charge of wells, water quality and IIRC, their certified pump guy program, was constantly boasting on a water treatment dealer forum of their success in avoiding contamination. I haven't seen him post in that forum lately but he doesn't mention the problems in the blog he does for a newspaper where he lives.

I just received one now, here is a copy of the subjects, the subjects in the email are links to the stories but don't work as a copy:

Top Stories for March 4, 2009 Today's Circulation: 18,036


Meds-in-water levels too low to cause harm: study

Credit unions take larger role in small-biz loans

Construction under way on water tech center

Chlorine plant security questioned after arrest

Aging nuclear reactor near source water a concern

Wanted: PCE source tainting CA wells

A week for fixing leaks

Waukegan, IL, gets the OK to drink from the tap

 

[BillH]

if the 1st check valve leaks, why not add a second?

Everyone seems agreed that if the check valve on the pump fails, it must be replaced.
So I'm wondering: mine started leaking slowly, causing the pump to cycle every 20 minutes or so. The pump is 180' down. For a quick fix, I put in a check valve near the pressure tank, and it seems to be working fine. If I pay someone to come out and pull the pump to replace the 1st check valve, I might as well replace the pump at the same time. Buy why not just continue to use the system with 2nd check valve, until I absolutely have to replace the pump ... ?

 

[Gary Slusser]

You are hiding the leak and that can lead to dropping the pump to the bottom of the well, causing the pump to run constantly 24/7 eventually, allowing air into the water line and out to your faucets, it can cause water to spray against the inside of the well causing dirty water etc..

You can use that new check valve to install it on the outlet of the pump, you don't need to replace the pump unless there is something wrong with it or if it is worn on the outside or simply based on its age. And at 180' wit ha leak, 2 guys can pull the pump if you don't have it on galvanized. If you do, the nyou need a tripod, backhoe etc. and a couple large pipe wrenches.

 

[Speedbump]

That leak could be a hole in the droppipe not a bad check valve. That hole will grow in size. If you don't wear the pump out first, the hole could get big enough to allow the pump to run and never shut off. Then your pressure just keeps dwindling until you have practically none at all or the pump just falls off the pipe and settles to the bottom of the well.

If I were pulling my own pump for any reason and it were more than 4 years old. A new one would be replacing it. I would not stick the old one back in. Most of the job is labor not the price of the pump.

I know Gary advocates people replacing their own pumps, and I see nothing wrong with it if your very knowledgable and have the right tools. But I have lost count on the number of customers that ended up with new wells because they tried to fix one instead of calling in a pro.

bob...

 

[BillH]

Thank you, both these replies are convincing ... I will replace the pump and fix the leak. I really appreciate the help! I had questions regarding the type of downpipe I should have in this well, and thinking that that was a different topic, I posted that question separately here:

https://terrylove.com/forums/showthread.php?t=27545

Thanks again!