I recently bought two appliances that need a cold water supply - a drinking water filter that mounts under/on the kitchen sink, and a self-cleaning cat box. Both come with T-valves that screw onto the supply valves, providing water for the appliances and the sink or toilet. The water filter T-valve can be converted to 3/8" or 1/2"; the cat box one is just 3/8".

I discovered that the supply valve threads in my house (built in '05) are larger than 1/2". I measured them with calipers, went to the store where I bought the water filter, and tried to find an adapter. Near as I can tell the house has 5/8" supply valves. The plumbing guy in the store was trying to help me; he seemed quite puzzled at first but then went "a-ha" when I told him I was in a mobile home. Apparently they don't use standard supply valve sizes for whatever reason.

Most annoying is that apparently metal threaded adapters from 5/8" to 1/2" or 3/8" just aren't made. The employee was fairly certain that they did not exist but helped me hunt through their selection just in case. No adapters, and this was at a Home Depot. The employee suggested I get the supply valves changed to standard ones.

The current supply valves are brass, and appear to be set into the house supply lines with some kind of adhesive. The supply lines bear no markings, but are beige plastic that is 0.635" OD.

1) Is there some special place where I can get the right adapters to avoid having to replace the supply valves? Female 5/8" to male 3/8". I recall reading somewhere online that you're not supposed to do metal to plastic on threaded adapters...? (this despite the fact that the fixture supply line ends are plastic)

2) Can I place the T-valves for the appliances further up from the supply valve, basically somewhere in the supply line that runs from valve to fixture? The sink supply lines are semi-flexible hard white plastic, 0.375" OD. The toilet supply lines are flexible soft white vinyl-like plastic with a crosshatch pattern, 0.515" OD. I would need 3/8" M and FPT with a slip fitting (think that's what it's called) for both sizes of fixture supply line, do these exist? Is there some other way to go about doing this?

In short: house supply line --> supply valve --> fixture supply line --> slip fitting / 3/8" MPT --> T-valve for appliance --> 3/8" FPT / slip fitting -->fixture supply line --> fixture.

3) Should I just replace the supply valves and the fixture supply lines? Do mobile home toilets have different supply line threaded connector sizes than normal? The one on mine is pretty fat, at least 5/8" maybe larger.

Basically, is there any way to make any of this work? Would it be something I could do myself (I've installed a kitchen faucet, that's about it), or do I need to hire a plumber?

If there is a mobile home supply dealer in your area, they will have those fittings. I had several mobile home rentals at one time, and went to the MH supply shops in our areas to get plumbing fittings, doors, windows, etc.

In a pinch with plumbing, I was able to go to the hardware and get brass fittings. It is okay to use brass on plastic as long as you use plastic compression rings, aka ferrules. The reason for this is that if you use brass ferrules, they will actually cut into the plastic pipe.

If you have a good hardware store in your area, you will probably do better than at a building supply.
Al

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Originally Posted by albinfla

It is okay to use brass on plastic as long as you use plastic compression rings, aka ferrules. The reason for this is that if you use brass ferrules, they will actually cut into the plastic pipe.

If you have a good hardware store in your area, you will probably do better than at a building supply.
Al

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Thanks. Don't know what a ferrule is, (I googled and could not find one in a plumbing context that shows where exactly it goes in a connection), but I figure a store employee somewhere can show me. I'm not sure what makes a 'good' hardware store... in my area there are the standard Lowe's and HD, plus Ace and maybe a few others.

I would try Ace first. If not, then HD or Lowe's might have them. I've attached a picture of a typical valve, with compression fittings. A tee or other fitting would have the same compression ring (aka ferrule), and compression nut as the valve pictured. If you can print the picture, I'm sure that they can help you at the store.

Attachment 11235

Hope that helps.
Al