What would happen if I just bypassed this garden water check valve?

You have water higher and you expect it to ignore an opportunity to get lower?

Yes, you are missing something obvious. If there is no check valve there, water can be drawn by vacuum back into the house. The elevation of the line is immaterial.

Backflow preventers are often required by code. If it is in your town, removing it is a violation.

do you really need it? Probably not for most people. What they do though, is prevent backflow or siphoning if you pressure drops. In the case of a line with lawn sprinklers, it prevents backflow of lawn fertilizer and dog crap to the drinking water system.

Most times they are needed in industrial or commercial applications. In the case of a pressure drop, a boiler or water tank could easily force water back into the system. Residential use, possibility is much less. But I'm not going to tell you to take it out. They can be rebuilt too.

Hi, It is the code where I live. I do't want to have even one in a thousand chance of drinking dirty water no matter what. I have them on outside faucets and in-line feeding sprinkler system.

Hmmm... the water goes lower all the time.

Otherwise, I'd have no water in my garden hoses.

It's the OPPOSITE direction that the check valve is for.

However, I can't imagine water ever climbing that high UP from the garden hose into the water tanks on the other side of the check valve.

Hmmm... that must be true because they bothered to put the check valve there.

Are you saying ALL houses which have a separate line for garden hoses than for the house, have a check valve ONLY on the garden hose line but not for the house?

Because I have only one check valve ... and it's ONLY for the garden hoses.

The way I know that is I shut it off (because it was leaking), and only the garden hoses stopped working.

So, is EVERYBODY's house designed this way?

I've never seen one of these before on a house. Certainly if they were in my old house, I didn't see them.

This new house (new to me anyway) has this 'backflow preventer' only in the line that goes to the exterior hoses and sprinkler system.

So what you said makes sense. It's to prevent the sprinkler system from being sucked back into the water supply.

So, I guess it's needed.

So I'll look up how to rebuild it then.

Yes. That's what it's on for me too.

It's only at the top of the hill, at the level of the bottom of the water tanks, and it's ONLY for the sprinkler system and hoses that are OUTSIDE the house.

The spigots on the house seem to be fed by the home water system, which is a separate pipe.

Someone said I could rebuild it - so I'm going to Home Depot tomorrow (and maybe Lowes) to find the parts to rebuild it if I can.

Jeez, just buy a new one.

That's probably not a bad idea.

I'm trying to figure out what it is so I can price it. And how it works.

For example, what's the purpose of the four female fittings?

There are some curious fittings on many of these backflow preventers. I had a sprinkler guy install a new system and he said they are for testing purposes and someday some code official might want to use them for testing, but he'd never seen it done.

I would not get hung up on that aspect. If you're really concerned, find what you think is a suitable replacement, regardless of the fancy fittings, print out the datasheet and take it to your local plumbing inspector and ask. That's the only way you'll know for sure, regardless of what anyone here thinks.

My guess on those four female fittings is one of two things:

1. you could run four above ground water lines to different zones in your yard or garden. It looks like they have quarter turn shutoffs for each one.
2. they may be for blowing out the system with an air compressor, but being that there's four of them and the height location in relation to the yard, this is doubtful. On my underground lawn sprinkler system, I have to blow mine out prior to winter so that the water in the lines don't freeze and bust the pipes.

I agree with the prior posts that the backflow preventer is necessary.

I have no idea. Best guess is for attaching pipes, no idea why you would want to. I also have no idea why there are fore and aft valves.

I do see what appears to be a clean out fitting (two, actually). If it were me I'd open them up and see if some gunk was keeping the valve open. If you replace it, all you really need to know is the pipe sizes to which the new check valve will attach. You will probably have to do some pipe fitting too - nipple & coupling at least - as it is not likely a new one will fit lengthwise properly. Cheapest check valves are PVC; brass is both better and pricier.

I just got off the phone with Wilkins Zurn Technical Support (aka Wilkins Water Works) at 1-855-663-9876

A new one is over seven hundred dollars.

So, while it may be easy to say to buy one, I would think a home repair is in order here.

Luckily, they make a 'repair kit', with instructions:

I called up Wilkins Zurn (Wilkins Water Works) technical support. They told me those four fittings are for testing purposes, as you had surmised.

I'm reading all I can on it from the datasheets right now since it's a $755 part with a $55 repair kit - but, as you know, repairing (fixing) takes more effort than simple replacement.

Wilkins Zurn 975XL Specification Sheet

OK. I don't disagree. It's there for a reason. I'm going to try to understand the thing and then repair it.

BTW, I can't tell if it's a 1" or a 1.5 inch opening because it clearly has a "1" stamped on each opening but it's just as clearly got a >1" pipe going in and out.

Here, for example, is a ruler next to the pipe and a yellow circle around the 1. LARGE:

Q: What size would you say this Wilkins Zurn 975XL actually fits?

I called Technical Support again: 1-855-663-9876x2x4 and I detail the answers so the NEXT person with a similar question can find the answers more easily.

Zurn Wilkins (they don't call it Wilkins Zurn) tech support confirmed the (1) indicates it's a 1-inch fitting even though the OD of the pipe going in is clearly (much) greater than one inch in diameter.

They told me to look for an additional (1") on the body and lo and behold, there it is (see this picture):

This repair kit comes with the thicker upper check valve spring, the thinner lower check valve spring, 3 o-rings,

They said that Furgeson Enterprises sells them:

Yeah, thanks, Donna.

You do realize that pipe is not really measured like it is called ? That is what is called one inch pipe will actually measuer about 1.3 inches outside diameter with a ruler.