Lawn Sprinklers & Bathroom Hot Water?

[sjelso]

I have what seems to me to be a strange situation. About 8 years ago, before we moved into our house (built around 1953) we had all the plumbing replaced/upgraded to copper and new water heater. The lawn sprinkler systems was already in place when we moved in.

To get hot water to the bathroom (farthest plumbing point from the hot water heater) we have to run the hot water for a few minutes (not unusual).

However, about 3 years ago, we noticed that we no longer had to run the hot water in the bathroom on mornings when the sprinklers run.

What could have changed (no work done) that now the sprinklers could affect the hot water system? It is almost like the sprinklers are acting as a hot water recirculating sytems.

Any ideas?

[jadnashua]

While the sprinklers are running and someone is watching them, shut the valve to the inlet of the WH and see if that affects the spray. It shouldn't, but if it does, you could have a cross-over somewhere that is allowing some hot flow to the sprinklers.

[Gary Swart]

Do you have a back flow preventer to stop cross contamination, and if you do, is is tested by a certified tester annually? I won't go into a lengthy discussion on why you should have a back flow preventer, but if you don't have one or if the one you have is malfunctioning, you are risking your family's health. These devices are required in most places, and where I am, they must be re-certified each and every year.

[sjelso]

I know there are some backflow protectors on the hoses but I am not sure about the sprinklers. This be affecting the hot water?

[Gary Swart]

When the water supply line tees, one branch goes to the house and one to the sprinklers. Sometimes referred to as anti-siphon, a back-flow preventer should be installed in the sprinkler branch somewhere before the manifold that splits the water into zones. There are different styles, but they prevent contaminated water from the sprinkler lines from getting into you domestic water supply. These devices will isolate the sprinklers from the domestic water. Some hose bibs will prevent this, but if you have a piped irrigation system, you must have cross contamination protection of some kind, and it must be working properly. You can not test these devices yourself. It takes specialized instruments that are expensive and require training to use.

[sjelso]

Okay..will have that checked..appreciate it.

SJ

[Redwood]

I'm going to agree with both of the 2 separate items discussed here.

#1 Yes, the irrigation system should have a backflow preventer installed on it. Check with your local authorities to see what is required and check to see that it is installed.

#2 The instant hot water when you use the irrigation system is a sign that there is a Hot/Cold coross connection somewhere. The way your house is plumbed makes this connection more pronounced as the pressure drops from the amount of flow going to the irrigation system.

This Hot/Cold cross connection is essentially what would exist if you had a utility sink with a hose bibb connection on the spout and had both the hot and cold turned on while the hose was connected but the nozzle was shut off. This would allow water to flow out of the hot and into the cold line when the pressure on the cold line dropped lower than the hot.

This connection can also occur in some single handle faucet valves such as Moen and Mixet.

[sjelso]

Very interesting..we do have single handle faucets..American Standard.

What is strange, is that nobody touched anything and then one day..it just started doing this.

SJ

[Redwood]

What have you got for tub shower valves?

[hj]

Do you have a concrete slab floor?

[sjelso]

We have a crawl space.

[sjelso]

We have Price Pfister shower valves