Need to stop sprinkler system from siphoning from water treatment

[sp00kster]

I am not sure if this is proper forum but any help greatly appreciated - Quick version

We are on a well - sprinkler system is the first plumbed outlet after pressure tank then on to water treatment system (chlorination). Problem I am having is that the sprinkler system when on is siphoning from the water treatment system. Basically watering the yard with heavily treated water. I installed a spring type double check valve as well as a pressure gauge for monitoring and regardless my efforts it still continues to siphon through the check valve especially on high volume stations. All fittings are brass 1" NPT.

I was looking at perhaps back flow preventers (guessing) - but there are many styles and do not wish to purchase wrong valve

Any help in this matter would be greatly appreciated

[dubldare]

First, make sure you have a pressure vacuum breaker installed where the irrigation feed leaves the house, prior to the connection to the sprinkler system. The critical-level (CL) of the vacuum breaker must be at least 12" above the highest point of irrigation piping. If this cannot be done (due to elevation), an RPZ is required. This protects your drinking water.

Secondly, a DCIAV (double check, intermediate atmospheric vent) style vacuum breaker would prevent the water on the house side of the system from migrating back to the irrigation system. An RPZ could also be used. Both the RPZ and the DCIAV provide an atmospheric break in the piping, meaning there is virtually no possibility for back siphonage.

Your problem sounds to be as one of inadequate supply for everything you are trying to do. I would surely hope you don't have a pump for the irrigation system, as that would explain a lot. Perhaps reducing the size of your zones (adding more, making each zone 'smaller') is your best bet. You most likely are exceding the flow rate of your well vs demand on your larger zones. Please don't ignore this part, as it is most likely the crux of your issue.

With all the examples above, and what you've already done, your system is 'closed' and requires a thermal expansion tank for your water heater. Make sure you have one.

[Terry]

http://www.wattsreg.com/prod_images/007QT.jpg (http://www.wattsreg.com/prod_images/hi-res/007QT.jpg)

I like to use a double check valve for irrigation backflow.

Series: 007
Description: Double Check Valve Assemblies
Size Range: 1/2 to 3 in. (15 to 80mm)

Series 007 Double Check Valve Assemblies prevent the backflow of contaminated water into the potable water supply. It consists of a bronze (1/2 to 2 in) or fused epoxy coated cast iron (2 1/2 to 3 in) body construction that is easy to maintain and service. Series 007 is ideal at referenced cross-connections identified as non-health hazard applications. Check with local inspection authorities for installation requirements. Maximum Working Pressure: 175psi (12.06 bar).

http://www.wattsreg.com/

[Gary Swart]

You're thinking right about the backflow preventer. These are required on public water supply systems. Basically what you do is tee the main supply line to feed untreated water through a backflow preventer for the irrigation and the other side of the tee into the treatment device. This will do two thing for you. You will not be irrigating with the treated water, and you will not be syphoning water from the irrigation side into you household supply. I don't remember the brand of backflow I use, but any decent plumbing supply should be able to provide a suitable one. In my city, I am required to have an annual inspection to verify the backflow is still performing properly. You won't have the legal requirement that I do, but I'd suggest you find a plumber that can test yours for you own safety. I pay $25 for my inspections.

[dubldare]

If I'm reading him right, he is siphoning water from the treatment system (house water) into the irrigation system. Any backflow device solely on the irrigation branch will not stop that.

[Cass]

A Watts #7 check valve installed between the hose bib / sprinkler and treatment system with the flow direction towards the treatment system will solve the problem. The sprinkler should have a backflow on it also.

[Gary Swart]

I stand corrected, Dubldare is correct. I misread the question. I wonder if a double check valve in the potable line might be the answer. In other words, a double check valve in both lines. This is a guess, I'd sure check deeper into this before investing in the valve, but it seem logical that it would work.

[sp00kster]

Thanks for all the responses - Guess I am still am a bit confused by posts. I will recap a bit to explain.

1st - water supply enters through basement wall into pressure tank
2nd - T's off immediatly (sprinkler - potable house water treatment system)
3rd - sprinkler system already has an anti-siphon valve outside to prevent potable water contamination
4th - Potable house water treatment side already has a Watts (Series: 7) dual check valve installed immediatly after T - to prevent potable treated water from siphoning into the sprinkler system.
5th - Between our well service, sprinkler service and water treatment service (all of which are pointing fingers at each other)

Guess what is confusing me is what is the difference in a back-flow prevention valve and dual-check / double check valve. If / when you go to Watts url (www.wattsreg.com) all are labled "back flow prevention valves". For the life of me I do not understand how when the sprinkler system is on it is able to siphon the potable house water back through this dual check valve (replaced twice), in the first place. Must be some serious negative pressure or something. I have no problem purchasing what ever it will take to stop this backflow just that I know from experience that it will take more than a Watts (Series: 7) dual check valve / back flow preventer.

[Cass]

How do you know it is backflowing/siphoning?

[sp00kster]

All of this was brought to my attention in the first place when we noticed that chlorinator was using an extremely large amount of chemical during the watering season. So we called our water treatment service company out and they are the ones that realized that the chlorinator was running while the sprinklers were running (due that chlorinator was wired into the well pressure switch (creating a very concentrated solution in the retention tank)). At the time there was not even the thought of it siphoning out to the sprinklers just that the chlorinator was running regardless whether it be potable water or sprinkler. So they sent plumber out who installed a single check valve, pressure gauge and a independant pressure switch on the potable water side. So I am told that now the chlorinator will only come on when potable water side pressure drops thus tripping the indepandant pressure switch and allowing the chlorinator to run with pump. He showed us by engaging the sprinkler system and the house pressure did not drop and the chlorinator did not come on. Later we found that it did work on zones 1 - 3 that were very low volume (pop-ups and drip) - until the high volume zones 4 - 7. As soon as any of these zones would engage the potable water pressure side would quickly drop and the chlorinator again would engage. I also used our water test kit to test for chlorine via the sprinkler system on zone 4 (5ppm).

I called our water treatment service company back out and they in turn sent plumber back out - he in turn replaced check valve with dual check valve. I was not home to test while he was here (still did not work). Now they are all saying that is best they can do. Now makes me wonder if he really was a plumber in the first place.

Any way you have now heard the long version and any help would be greatly appreciated

[Cass]

I am wondering if

#1 the chlorine is affecting the check valve some how.

#2 if there is a cross connection somewhere that you don't know about.

[sp00kster]

Chlorine can only get to the valve in the first place because of siphoning. I have attempted to create a diagram in Microsoft Word as an illustration - I will attempt to attach.

[Gary Swart]

The only thing I can think of is that the check valve is not functioning. The backflow I use is exactly the one Terry pictured earlier, and should do the job. I would have it tested to make certain it is functioning properly. They can fail, that's why my city requires an annual test.

[sp00kster]

Ok - Will replace again - a big thanks to all of you for your input. Ever need any advice on replacement windows or doors feel free to give me a shout and perhaps I can return the favor!!!

Best Regards

[Gary Swart]

NOTE: I was only suggesting you have it checked. While this seems to me to be the only logical possibility of the cause of your problem, I'm sure as heck no expert! Any irrigation supply company should be able to test the backflow valve. If it's working OK, then I'm stumped.

[hj]

Either you are misstating the problem, or you have a different problem than you describe.

1. Any "backflow" device will prevent the irrigation water from flowing into the house. It will not prevent anything ahead of it from flowing into the sprinkler system.

2. The irrigation system should have a positive pressure almost equal to the house pressure, especially at the connection point, so siphonage cannot occur.

3. If the system is piped so that aspiration can occur and draw the treated water from the chlorinator, then that is a different problem and needs a different cure than a backflow preventer.

[sp00kster]

HJ - I am not sure exactly on the aspiration part in #3 but as for the rest of #3 all is correct and is confirmed with a water test of the well water at the sprinkler head as well as simply watching the potable water side pressure gauge drop to match the well pressure. Using chlorine free test strips. That the sprinkler system is siphoning / sucking / drawing whatever the best term would, chlorine treated water through the dual check valve. There is a Word attachment with a detailed diagram a few posts back - perhaps may shed a clearer picture. As for the other examples they are not relative to my problem. The sprinkler line T's off 3' prior to the potable water dual check valve and chlorinator is another 3' downstream.

[sp00kster]

just adding one more note as an example - Potable house water pressure at 50lbs and holding and does not deviate on 1-3 low volume sprinkler stations(well pressure during is at 45lbs constant. Then comes zone 4 (well pressure during is 35lbs constant), potable house holds at 50lbs for about 30 seconds then slowly starts dropping soon matches well pressure at 35lbs - also trips independant pressure switch when it hits 35 pounds thus starts chlorinator.

I can actually stop the siphoning by going all the way accross the room on the other side of the water softner where it goes into the house and close the house supply shutoff ball valve - the potable house pressure stops dropping immediatly and sprinkler continues on. As soon as I open house valve back up pressure continues to drop to well pressure.

The plumber that installed the dual check confirmed what I have posted but said he had never seen anything like it and would have to get back with us. Later he - water treatment company left message on answering machine stating they have done all they could do.

[dubldare]

A RPZ on the house side of the irrigation piping will prevent treated water from backfeeding to the irrigation system.

It will leak from the relief/drain when 4-7 are on. This is the price you pay. All RPZ's will leak if supply pressure drops too low.

Either size zones 4-7 the same as 1-3 or deal with high pressure going to low.


Additionally, you should have a relay to prevent chlorinator operation when the irrigation system is running. Time the irrigation system to run at night when you're not using water in the house.

[hj]

You cannot have siphoning with your system. You either have backflow because the pressure downstream from the chorinator is higher than the dynamic pressure at the irrigation system's tee, which is implied that it starts when the house pressure starts dropping, or your flow is so great that it creates aspiration. Siphonage could only occur if there were a way for air to enter the system past the chlorinator as the treated water is drained away, and even a back pressure could only occur until the two pressures were equal, and since water is not compressible, that would occur very quickly. As stated previously, your description implies a different problem.

[sp00kster]

Seems the more I attempt to fix - the more unanswered questions arrise.

I removed the dual check valve to have tested / replaced - the house water would not quit draining out - noticed after long period of time that water was getting warm, then hot. I had to finaly had to go close the shut off valve at the hot water tank upstairs some 30' + away. This does not seem right.

I have described to the local plumbing supply house of my plight and they were as supprised / disbelief as the most of you all were / are. They talked well over my head with many ideas then sold me some sort of inexpensive flow meter / gauge to be installed right where potable water enters house past all water treatment. They explained to me in laymans terms to my best understanding that I needed to find out first if it was truely drawing off of the house water and not simply de-pressureizing (sp) the water conditioner tanks (ie.. carbon, green sand and softner tanks). As well I should lower both pressure switch settings to more truely match the well pump capacity.

I am about to throw my hands up - I now know more than I ever wanted to know about plumbing and at the same time know less than when I started. I think it is perhaps time to get out check book and start getting estimates to find out what is going on here.

Thanks everyone!!

[Marc]

I noticed one other thing... I thought chlorinating water before a softener was a bad idea? Perhaps I'm just mixing the order up in my head.

[sp00kster]

Nope - chlorinate first then syn. carbon to remove chlorine then softner

[rickford66]

Just wanted to chime in with an uneducated question. I've been reading some of these posts trying to learn something. I've also looked at the diagram here and I wonder if the retention tank is similar to the pressure tank. Does it also have an air bladder in it? If so, it would explain the slow bleed of pressure... but like others have said, the check valve must be leaking.

[Gary Slusser]

A retention tank with captive air wouldn't cause the problem as long as the check valve was sealed closed B U T...

I wonder if the water treatment is backwashing and regenerating while the irrigation is running; especially the largest zone.

If so, the irrigation should be changed so it is not running at the same time; at least the largest zone.

Assuming both are running at the same time, then the check valve must open to feed the water treatment/house so it can backwash and regenerate. That will/can/could allow chlorine backflow back through the check valve. And a substantial amount IF the flow to the large zone is equal to or greater than the DLFC gpm of whatever piece of water treatment is in backwash. A softener will have the lowest gpm (drain line flow control) as little as 1.5 but as much as 3 gpm, but the carbon filter can be as much as say 5-10 gpm. The greensand filter is redundant and should not be needed with a chlorination system.... but will flow at maybe 5-10 gpm also.

AND the pressure tank is supplying both water uses, irrigation and water treatment, while the pump is NOT running. Meaning that the backflow will be higher when the large zone is running with say the the softener is in backwash. So most flow from the pressure tank, and then the pump, will be to the large zone as opposed to the softener. And when the softener is in slow rinse/brine draw (for up to an hour plus), the flow is .25 gpm (read point 25) and the check has to open to supply it.... and stays open, so in effect there is no check valve when this happens!!!

So the question is, does back flow happen every time the irrigation is on or only sometimes; which would be when the softener is regenerating? Which can be from every night to every 2 or 3rd night and I could see the irrigation running on about the same schedule....

A leaking toilet or RO or ice maker would also cause a small flow and the pressure tank or pump to feed it through the check valve.

I haven't spent a lot of time on coming up with this theory, but it seems logical and very probable especially IF there is no other explanation as to how chlorinated water gets backward through a check valve; regardless if it is a double or X stage check.

So change the time of irrigation and see the outcome. Or timer the power to the pressure switch controlling the solution feeder so it can't run while the large zone is running.

Another fix may be to tap off the irrigation ahead of the pressure tank and control the pump with a pressure switch on the irrigation line. I'm not sure of this though, and would have to think it through more than I have now.

Just change the time these things operate and I think that will solve the problem.

This problem will have nothing to do with the pump, its capacity or the pressure tank or the pressure you operate the system at etc..

Ah yes... The more I think on this, the more I see the check valve open feeding the water treatment while the irrigation is on...

That's until I think of testing the irrigation water and finding chlorine and none of the water treatment is in backwash or regeneration.... ummmm

Well, at least you know you don't need the greensand filter. :)

[rickford66]

How can the check valve be open and still allow water to flow backwards through it? What I mean is, water will only flow from higher pressure to lower pressure. If the higher pressure is on the treatment side and the lower pressure is on the irrigation side, then how can the valve be open? I'm a newbie, but I think a spring check valve requires a small amount of forward pressure differential before it will even begin to open. The resting spring pressure has to be overcome to unseat the ball. Going out on a limb, I think the valve either has to be leaking, or there is another path. Is there a service bypass that might have been installed incorrectly that doesn't appear on the diagram?

[Gary Slusser]

Yes I've thought about another source (like a cross connection) feeding the larger zone too but... this problem goes away and there is no change in the flow of the large zone when he shuts off the water to the house AFTER the water treatment.

For water to get to the water treatment equipment, whether the pump is running or not, the check valve has to open.

During the brining cycle of both the greensand filter and the softener, which lasts up to 60+ minutes normally, the flow is usually at .25 gpm. During backwash. All 3 pieces of equipment will be flowing for at least 6-18 minutes at up to 10 gpm. During final rinses, they will be flowing at up to the same 10 gpm for 4-8 minutes. A backwashed only filter will usually be done in 20-30 minutes. A softener will take an hour and 15 minutes to an hour and 30 minutes.

When the check valve opens, and yes most check valves have a cracking pressure of up to 5 psi, the chlorinated water can mix with and flow backwards due to the flow to the irrigation. Especially with a single check check valve... they invented the double check to prevent that BUT... again, both checks have to be open or the water treatment equipment can not get any water.

I can't recall what the term for this is but it is used in backflow prevention courses. I've seen colored water demos of the problem. You'd be surprised, I was amazed, by what water currents exist inside pressurized water pipes when valves are opened and closed on main lines and branches of the same system. The display used clear PVC pipes with clear and colored water and backflow currents would flow backwards against the flow direction for quite a distance.

Here we have two simultaneous flows in opposite directions with varying pressure and pressure fluctuations in and between both sides of the check valve. Both sides actually go to open discharge, or at least the house side does, with very low flow and pressure individually, and then the pump comes on. Thereby there should be a lot of currents formed at/before/in/after the check valve as it opens and closes.

[rickford66]

Kind of like a riptide, eh? If you've seen it, then I believe it, but I sure can't see how. :O)

[sp00kster]

Well have installed a pressure vacume breaker in place of the double check valve and seems to be doing good. For the posts about the softner system regenerating during the irrigatiing (causing the back siphoning) - all regenerating is timed during late night. I am now going to attempt the last part of this problem but not exactly what area to post this question.

Now that siphoning appears to be stopped. I need to figure out how to shut off the chlorinator when sprinklers come on as not waste chemicals as well as excessive wear on injector. Chlorinator is 220vac liquid injector model that is wired directly into the well pump switch. So it runs whenever the pump runs - regardless house or irrigation. My thought was an attemp to reverse the normal use of a PSR (pump start relay) wired to the sprinkler controller. So instead of using the pump start relay sending a start signal to the 220vac well pump but rather a stop signal to the 220vac chlorinator. My problem is that standard PSR's are normally open I need to either find one that can be modified to be normally closed or possibly used in conjuntion with a DTDP (double throw double pole) relay as to reverse the normal usage.

As I said before any ideas on what might be the best forum for posting this please advise as well feel free to chirp in with any ideas.. As you can tell I am not a plumber and/or an electrician just too damb poor and try to do as much as I can myself.

Again a big thanks to all!!

[jadnashua]

If you can find a normally closed relay, put it in series with the power to the chlorinator. When the irrigation system is running, have it also open the new relay to the chlorinator.

[Gary Slusser]

Well have installed a pressure vacume breaker in place of the double check valve and seems to be doing good. For the posts about the softner system regenerating during the irrigatiing (causing the back siphoning) - all regenerating is timed during late night. I am now going to attempt the last part of this problem but not exactly what area to post this question.

Now that siphoning appears to be stopped.

I may be misunderstanding, but if the two systems weren't using water at the same time... there shouldn't have been a back syphoning problem; but finding chlorine in the irrigation water said there was a problem. Are you sure the solution feeder is working now?

Now that there is no problem, why do anything, especially something electrical?

I don't know of a better place to continue this than here in the same thread.

[sp00kster]

Even though the back-siphoning appears to be stopped. I would like to remove the secondary pressure switch and wire the chlorinator back directly into the well pressure switch. But I cannot without it constantly running when the sprinkler system is on making a very very strong consentration (sp) in the retention tank approx 100 fold stronger than it should be - much wasted chemical, excessive wear on injector, etc....

Seems it would be much better just to have it electrically shut down whenever sprinklers come on.

[Bob NH]

This seems to be reduced to the same question with slightly different words that you asked in the Irrigation forum with the Normally closed PSR? thread.

Does that answer about how to hook up a DPDT relay solve the problem?

I don't know what controls your sprinkler system because you haven't described that. But turning off the chlorinator depends on getting an electrical signal of some kind when the sprinkler is running.

If the sprinkler is running on a timer that drives multiple independent valve curcuits, and therefore doesn't give you a single signal when it comes on, then getting an electrical signal to shut off the chlorinator may be a little more complicated, but that is what you need to do.

Describe the irrigation system a bit more. If you can't get one signal when the irrigation systems comes on, how many independent valve circuits do you have?

[sp00kster]

Yes same question in other forum - Another member posted that a flow switch would be a good alternative and I think that I will do some research on that lead.

Thank everyone for all your help - this is a super forum!!