Pressure System Problem

I am in the process of renovating my in-house water system as a result of having to replace my pressure tank. The system utilizes a cistern as a reservoir, rain collected off the roof as the supply source, and a submersible pump located in the cistern. The old in-house system consisted of a 5 micron filter followed by a pressure switch, pressure gauge and the pressure tank. This system worked fine.

For a variety of reasons influenced by the off-the-roof source, I decided to change the location of the tank and add a second in-line filter with the result that the logistics of the new system are that the water passes through a 30 micron filter, a 5 micron filter, followed by the pressure switch and gauge, and then the new and larger pressure tank. This system results in off/on/off/... cycling of the pressure switch.

A call to the customer service line of the tank manufacturer informed me that the tank and pressure switch had to be before the filters. This has been confirmed by the very informative discussions I have read on this site.

Okay, I can revamp the layout of the in-house system and have a workable system. However, I am concerned that the system will eventually have problems because of the potential for the tank, pressure gauge and switch becoming clogged.

So my questions are:
Is there any way to protect the gauge, switch, and tank? Do I need to worry about it?
Why did the old system work without the oscillating problem?

Thank you for suggestions.

What and how much of it is in the water that could block the switch, gauge and nipple? Tanks can't block up and dirt build up can't hurt a tank.

I've seen very dirty water not block those things.

Those things usually take a long time to block up, if they ever block up.

The flow rate of the new cartridge is too low for it to allow water through it fast enough; pressure builds, the water goes through the cartridge and the pressure falls and the pump comes on, and then off and then on.

Thank you, Gary, for your response.

What gets into the cistern is mostly fine matter (dust, dirt) that gets washed from the roof by rain and is too small to be caught by the screen filters that are in place in the eves. The filter becomes quite dirty over time and I probably replace them about every 5 weeks. The cistern water is not ingested, we use bottled water.

Over the years (more than 25) I have had to replace the pressure switch periodically but the basic reason for this is that the points have become burnt to the point that the bad contact results in the pump not coming on. I have never found any source from which to buy only new points, probably because there is not enough money in it. I have never really inspected the switches to see if they were plugged. I have also had the pressure gauge stop working, why I do not know, but this does not affect the operation as I am sure you know. But in all this time both the pressure switch and gauge has been located after the filter.

Is the pressure differential across the filter more than 20 psi, which it must be for the switch to come back on and continue cycling on and off??

Would the system operate properly if I just put the switch before the filters and left the tank where it is now, where I would really like to have it?

I have tested the system with the cartridges removed and it works fine. With only one cartridge in place it has the same problem.

And why did the old system not have the oscillating problem?

Thanks again for your experienced suggestions.

You're welcome. I can't answer why it worked before and not now except to say the cartridge may be mislabeled etc. etc.. The present design isn't working now and as you see, without the cartridges it works fine. That says a pressure loss across the new cartridges sufficient to cause the on/off problem for the pump. Which if left alone will probably burn the switch points or ruin the pump.

If it were mine, or I was doing this for a customer, there would not be any disposable cartridge filters, I'd use an automatically backwashed mixed bed filter and it would not be between a pump and its pressure switch.

Pump Preesure Problem

Thanks again for your comments, Gary. I am not familiar with the type of system you mentioned. Could fill me in? What does it consist of; is it complicated; what costs are involved? I will be going ahead with the changes using the disposable filters, but I always like to learn new things.

Thanks again.

They work like a water softener or iron or sulfur filter.

Thanks Gary, I'll look into it more.

I will reconstruct my system tomorrow and will let you know how it works.

Good travels.

Pressue System Problem

System has been reconstructed with filters placed after the pressure switch and gauge, and works fine. No on/off oscillating.

The system will work as you have described but you will need to deal with another situation as the filters reach capacity.

Most cartridge filters can be used with pressure differential up to 25 or 30 psi. As you reach end-of-life you will start experiencing large pressure losses when you have high flows, and changes in flow rate will cause large changes in pressure. When the washing machine turns on or the toilet is flushed while someone is taking a shower you will see a severe loss in flow.

A solution to that problem is to operate the pressure tank at substantially higher pressure (say 50/70 psi) and use a regulator after the filters set at 40 psi. That will reduce the effect but you will have to change the filters at less than their most economic life to get satisfactory service.

Another solution is to put a second pressure tank after the filters, leaving the pressure switch on the first tank.

When you are using roof runoff the water should be disinfected as well as filtered. Roof runoff is always at risk of biological contamination (think of birds and small animals). There will be biological growth in the stored water if it is not disinfected (usually chlorinated).

The following may be considered it you are into real DIY projects, which is often the case (by necessity) for people who collect rainwater for their household.

A good way to filter is to collect the runoff into a collector tank (ideally at a higher level than the storage tank) and let it run through a filter by gravity. Since the filter can operate for a long time after the rain stops it can have lower GPM capacity. An old swimming pool filter might be a good candidate, or a simple sand filter a lot like a sand box with drains.

Thank you, Bob for your informative comments.

As mentioned, I have now put the switch in front of the filters and it has been working okay except for for one occassion when it went into an off/on/off oscillation, why I do not know. I believe that the only demand at that time was as a result of a toilet being flushed.

One thing that I should have clarified was that the pressure switch [Square D]is located about 7 feet from the tank, followed by the gauge, and that the spread between the on/off settings shown by the gauge is only 10 psi and not the normal 20. According to the tank manual the distance between tank and switch can be up to 10 feet.

Also, and maybe most importantly, for physical layout reasons, my set up is like an F, with the source coming from the middle, the tank being at the bottom, and the demand side at the top. So the flow does not go from the source past the tank to the demand side. I believe that the fluid dynamics of such a closed system under static conditions are that the pressure is the same throughout the system. However, I am not sure how such a set up is affected when a demand is put on the system and filters are put into the equation. It seems to me that the flow to the tank and the pressure from the tank are in opposite directions and that may cause a problem, depending on the demand requirements. For this reason I have decide to change the flow so that it is from source to demand past a T connected tank.

I agree 100% with your comments about the water conditions. However, as stated we do not consume the water, and use bottled water for drinking purposes, and have done so for more than 25 years without problems.

Your comment about a collector tank is very interesting, but not viable for our location which has a shallow soil depth on top of limestone. I am lucky to have enough depth for the cistern tank to prevent freeze up in the winter, and then I have my intake pipe wrapped with a heat coil.

I would be interested in hearing your thoughts re the fluid dynamics of the current system.

Thanks again.

Pressure System Problem SOLVED!!!

I had stated on my previous posting that having put the pressure switch in front of the filters that the system was working okay save for one occasion in which there was an off/on/of/.. cycle. But low and behold today when I was catching up on my laundry, the system reverted to its old self, and during the first three loads there was an oscillating problem every time at certain points of the wash cycle which seemed to be when the washer was terminating a demand for water.

As I had also mentioned the pressure switch I was using was a new Square D (9013FSG, 2M4, Ser B) which only had a 10 psi difference, not the normal 20 psi, between off and on.

I did a load with one of the two filters (the 30 micron) removed, but had the same problem.

I was totally frustrated by this time and decided to try the old Square D switch. This switch was operating with a 24 point psi spread between off and on, and handled the 4th load of laundry without a problem, with both filters in place, and during some of this wash cycle, at times when there was a demand for water by the washer, I also had a garden hose running fully open. Not only did the pressure switch not go into oscillation, the pump exceeded the demand and built up the pressure until the switch shut off smoothly.

So I have concluded that the problem all the time was due to a faulty pressure switch.

Now the only difference in the two switches is that the newer switch was made in Mexico, while the older switch was made in the USA!!!

Tomorrow I will inform Schneider Electric, the US firm that produces the Square D pressure switch, and return it to Home Depot where I purchased it.

I hope all of this will save someone else the time and frustration I (and my wife) have gone through.

Thanks again to those that made an effort to help, and especially to Terry for this site.

PS: I did not change the flow as I stated I was going to do in my previous posting.

Yes the F should be changed as you stated. And the 10 lbs differential switch was part of the problem too; especially after the filter cartridges loaded up a bit and the pressure loss increased.

Thanks for your input, Gary. Since it is running fine now I will leave it as it is for the time being and get on with other priority to dos.

BTW, burnt points in the switch says excessive cycling. So I'm not sure that the system worked as well before as it will now with the filters after the pressure switch.

You may be correct, Gary. Perhaps at some future date when I have nothing else to do and am bored, I will rearrange the set up just to see.