Plumbing Question

I am not sure that I am picturing your setup right, but I do have some experience with this type of a setup for this and other applications. I have only done manually operated setups, but changing them to automated setups would not be very hard at all.

I am not sure how you are planning to use the diverter valve, because those are usually designed to flow water either one direction or another. You can’t usually have water flowing through all three directions at once or have it going in two directions and out one direction after mixing. My best guess is that you are trying to hook the hot water up to one side of the diverter and the cold to another and then turn the valve ever so slowly until you get the right temperature coming out the third direction. That will work to a point, but will be extremely tricky, because even the slightest change in the diverter valve will change the temp of the outgoing water quite a bit. Some diverter valves also don’t allow mixing at all, because there is no position in the swing of the valve that allows all three pipes to flow at the same time. Most of them that I have seen work where one output direction is turned on and then you turn the valve a little and it turns off the first output and now nothing flows. Then if you keep turning the valve farther, direction number two turns on. What I am trying to say is that there might not be any overlap to allow for mixing.

An idea that has worked well for me would be to use simple spigots on both the hot and cold water to adjust the flows of the hot and cold individually. Then after each of the hot and cold spigots, have a 90 degree shutoff ball valve on both the hot and cold water. Then combine the hot and cold water feeds into one pipe that goes to the aquarium. (If you want to automate it instead, use solenoid valves instead of 90 degree ball valves after the spigots and turn them on and off via a switch or timer.) Remember though that you must have a manual or automatic shutoff valve on both the hot and cold water line separately before they are plumbed together and become one pipe that is sent to the aquarium. If you bring the hot and cold lines together before the shutoff valve in order to save yourself from buying a second valve then a problem occurs. When the flow to the aquarium is shut off, the hot and cold water pipes will still be connected to each other through the two partially open spigots. Water will take the path of least resistance to get to any point, so if your cold water line for instance, has less pipe resistance than your hot water line (or vice versa) and you turn on the hot water somewhere else in your house (example- Bathroom sink nearby) the cold water could be pulled through this setup and into your hot water pipes. This would cause you to only end up with cold or lukewarm water at your bathroom sink instead of hot. After looking at the thermostatic valve that you have in the second link, it looks like it is possible that this valve could cause the same problem that I just mentioned unless you have a shutoff for both the hot and cold water before the thermostatic mixing valve. In saying this, I am assuming that since you want an automated setup, that you are wanting to just set the thermostatic valve at the correct open position and then leave it, instead of shutting it off each time and then having to reset it with each water change as you would for a regular mixing valve like on the average shower.

The nice thing about this setup is that once the main spigots are adjusted for the correct water temperature initially they don’t have to be touched at all and the water will always stay within a few degrees of the initial setting. Even worst case I just need to tweak one of the spigots a few degrees or so and that's it. That small temperature fluctuation has never caused any problems with the fish in my three tanks when doing a 50% water change. This accuracy in temperature is assuming though that you don’t change the water temp setting on your water heater and forget to adjust accordingly, or try to do a water change right after a long shower has used up all the hot water, haha. There are always a few trade offs when you are aiming for simplicity like I do, but I think they were more than worth it for this application. With the thermostatic valve you wouldn't have to worry about those issues, but it will cost you. Most of the thermostatic mixing valves I have seen are around $125 each and up, and then you need the cost of the solenoid valves on top of that to turn the water on and off automatically. That's why I don't mind initially setting two spigots and flipping the two manual ball valves myself during water changes, haha. They are only around $3.00 or so each.

In the picture I link to below, if you want to have cold water always continue over to the existing cold water spigot on the other side of your wall, just make sure that your existing spigot is fed from the cold water pipe anywhere in the line before the cold water spigot in this drawing. I hope all of this makes sense and good luck. -Jeremy

That Honeywell valve is very interesting, but they provide so little information about it I can't tell if it is even possible to use it for 75F water. And, it doesn't say it holds the temperature even if the hot water pressure drops because someone else is using hot water in the house. If it works like a shower valve of the type that holds a constant temperature, it would work fine for what you want to use it for. In fact I have been tempted to hook up a shower valve for my water change system. This Honeywell valve is smaller and looks better, so I hope someone tries it this way to see how well it will work.

You could easily connect this so the outside hose bib continues to get only cold water, while the aquarium gets warm water. Just think about it some more.

I think I understand what you are trying to accomplish.

You are adding water from a cold source only. The supply for that cold source comes from a mechanical closet (probably near the water heater). This is also the source for your hot water. So the thought is to introduce hot water to the cold line only during water changes, thus making the cold water line a luke warm line.

I think Jeremy has hit on the head. But this is problematic. While the hot source is constant, the cold source is not due to seasonal changes. So the mixing solution will change but not that much where it would be a headache. His thoughts are the most effecient though. You don't want the valves on the cold side though. Since this flow is constant. The double valves on the hot side is brilliant though. That way you have one valve as on/off and the other as a preset for amount to mix. So you just tee off the hot water creating a supply line with dual valves into the constant cold line.

Although your mixing line (cold source) will never get above CPVC rated temperatures you need to make sure you use hot line rated CPVC couplers/adapters and valves on the hot line.

The thermostatic valve would not work in your application. It works in the opposite direction of temperature and most if not all have a minimum temperature before they close (typically 90 - 95 degrees F). They allow you to introduce cold water into the hot supply line to reduce temperature to avoid scalding, while allowing you to keep the temperature high in the water tank itself. They shutoff at non threatening temperatures. And there shutoff point would be to warm a water to use for water changes.

If I am picturing what you are saying the same way that you are, I think that might work. I am picturing you basically splicing the hot water line directly into the cold water line somewhere before the outside spigot, and then having a ball valve on the hot water line right before that splice to adjust the flow of hot water going into the cold water pipe. Then you shut off that ball valve to mechanically shut off the connection between the hot and cold water lines when you are not filling the aquarium. Then you hook the aquarium hose up to the existing spigot, turn the spigot on, and get aquarium temp water at the aquarium through the now cold water only spigot when doing the water change. Then if you flip the ball valve to the off position when finished filling the tank, the spigot once again becomes only a cold water spigot that still has the full flow capacity.

That could work, but I have not tried it exactly like that before. Theoretically, if you have both the hot and cold water pipes directly spliced together with no restrictions, then you would have a perfect 50-50 mix of hot and cold water coming out the pipe with the mixed water after the splice. In practice you only need around 1/3 of the water to be hot in order to raise your cold water up to aquarium temperature, so having the adjustment valve on the hot water line to restrict its' flow some to achieve this ratio would work. You might consider doing the same thing except combine the two approaches to make it more user friendly. Just tap the hot water into the cold line like you were saying, but have a screw type of valve like a regular spigot on the hot water in addition to the ball valve. Just have one right after the other. I am just nervous about the ball valve's ability to finely adjust the flow of hot water, because they are really made more for an on-off application only. A screw type of valve would allow you much more control over mixing. Then you could do the same thing with setting the screw spigot initially and leaving it alone and only using the ball valve right after it to turn the hot on and off. That way the temp remains set between water changes so there wouldn't be any adjustment necessary each time.

This setup would pretty much be exactly in the middle of what I initially gave you in the drawing and what I think you are saying in your reply, and it would give you the best chance of making the setup work well enough to be an asset rather than a possible hassle.

One thing that might be a problem, is that this setup might be much more sensitive to any line pressure changes while it is operating. When you open the existing spigot at the end of the line right at the tank, depending on how far you open it that will change the line pressure between your mixing setup and the spigot you are adjusting. For instance, if you just open the hot water ball valve to connect the hot and cold water mechanically, then nothing actually happens in the lines until you open the other spigot that you have at the end of the line by the tank. Only then is a pressure differential created, and the hot and cold water begin to mix and be pulled towards the aquarium. The more you open the existing spigot at the tank, the greater the pressure differential becomes between the hot/cold water and your mixed water. You will probably find that the water temp changes not only from how you set up the system initially, but also from how much total flow you are pulling through the system as a whole. That could make it more of a hassle for trying to make this setup work well over time without a little fine tuning every time you use it. I don't think it would be that big of a deal, but it would be an issue that would make things a little less consistent and repeatable each time you do water changes. That would essentially be creating with two valves exactly the situation one encounters with their single handled shower valves. On the shower, if you pull out the handle to turn on the water to a certain pressure and then rotate it left and right you can fine tune the temp, but if after you reach the right temp you decide that you need more water flow and pull out the handle a little more it is very rare in my experience that the temp doesn't change a little and need to then be adjusted again. Changing the flow with the existing spigot at the tank would be the equivalent of moving the shower handle in and out. I hope that makes sense.

This setup could work, and to be honest I think it is worth a try, because it uses the same parts (and less of them) that you would need for a different setup like the one I initially drew, and it would be very easy to hook up, so all you would be out is a little time if it didn't work well.

If you do find that your temp changes due to both valves, maybe just draw a black line on the top of the spigot (at the tank) and for instance always turn that valve on two and a half turns so that way your flow rate is almost exactly the same every time you fill the tank. Then you could probably end up with a more “set it and forget” it type of water changing system to where all you do each time is flip the hot water ball valve, and turn the main aquarium spigot the specified amount of turns to set the flow rate, and then just do the opposite to turn everything back off.

Good luck, Jeremy

Here is what I was referring to about how to install the Honeywell mixing valve:


That Honeywell valve should hold the outlet temperature the same even if the cold water pressure varies, but if the cold water temperature varies widely, it may not hold the temperature constant. I'm not sure if it works like a shower valve, or if it has a temperature sensing actuator for the mixing function. In either case it should work well enough.

You could install a throttling valve in the line just before the aquarium so you can control the flow rate of the entering water.

That would work also Hoppy.

He would need the "C" model. I located a installation manual for that product.

http://www.houseneeds.com/Shop/manuals/honeywell_am1manual.pdf

But if I understand his situation correctly the closest hot source is the mechanical room. To mix at this point warms the cold water constantly for the whole house cold water. So he would need a on/off valve prior to the thermostatic to only add hot water during water changes. Otherwise he would be wasting hot water.

Here is a picture of what I am saying in case my explanation is too confusing. Let me know if I am assuming something that doesn't fit your application. -Jeremy

I think this is what he is describing....To cover all avenues.



A: Mechanical closet.
B: Cold Water Line
C: Exterior Spigot
D: Interior Spigot in closet used to supply wc
E: Cold water continuing to rest of house
F: Hot water source feeding whole house
G: Water Closet
H: Ball valve on/off
J: Temperature setting control valve

So the available hot water source is in the mechanical room. Mixing here then adds hot water (F) to the whole house cold line (B) while using spigot (D).

If this is the case then the use of either the thermostatic after a ball valve or two ball valves teed off of (F) tied into (B).

Actually in this case the thermostatic would not work. Unless you looped in cold water prior to the valve.

I updated with (K).

(K) would need to be a cold water input source for mixing. No valves would be needed in this loop. The thermostatic should close due to hot water pressure loss when the ball valve is shut off upstream (H).

You would have to check the manual how that valve handles regaining pressure and loss of temperature near the temp sensor.

Dual spigots would be IMO the easiest setup, and in the long run less proplematic, and cheaper.