running 3 bays on 3/4" water service

[Dan-Ark]

Have a 3 bay SS with 3/4" service. A customer stopped me about a month ago and said he and another customer were using the wash just fine. Then a third pulled in and when they were all washing, all 3 bays lost water pressure. I have a pressure gage on the hot water to my supply tank feed that was reading just over 40psi, until I opened one of the float valves on the mixing tanks and it dropped in half. opening 2 at the same time dropped the pressure to around 5psi. Contacted the city and they said it should be closer to 100psi, they checked it and said I had a leak. Sure enough, a leak in the copper under the equipment room. Fixed that and pressure went to 80. I thought all was good, but still getting a big drop when anything turns on. Yesterday, while cleaning bays, noticed the soap was weak in all 3 bays. long story short (maybe already to late to make this short). tried running soap (HP Hot water) in all 3 bays and ran out of water. I think the dema 440 is not sucking in enough chemical when the pressure is so low and mixing a weak premix of soap. From all I can tell, a 3/4 inch line should run 3 bays up to about 4 or 5 gpm each. the service is now all pvc from the meter to the equipment so i wouldn't think I could have a collapsed PVC line without a crack and leak. Do I just add a pressure tank to get some reserve for the rare occasions all 3 bays (very low volume wash) are in use? Is this kind of pressure drop typical? maybe the citi line has a restriction on their side of the meter? any ideas? We are just getting the clientele buildt up so having lots of soap, and pressure is high on my list. This wash has never done well for the last couple owners and now I am starting to think maybe this has had something to do with it.

 

[cantbreak80]

Your water softener might be the problem. Try by-passing it and see what happens.

 

[Dan-Ark]

Your water softener might be the problem. Try by-passing it and see what happens.

Thanks, no water softener at this location. City supplies soft (but expensive) water.

 

[Dan-Ark]

have noticed some discharge out of the RPZ which I assume is due to the pressure drop and may indicate the drop is ahead of the supply side of the RPZ?

 

[2Biz]

Do you have any Cast Iron connected to Copper or Brass in your main water supply? I replaced my 2" meter with a 1" meter to save on minimum water charges...Years ago my wash had an auto in one of the bays which probably needed the 2" main. I was paying based on 33,000 gallons minimum with the 2" supply. ...I don't come close to that even with weep. A 1" meter dropped minimums to about 6,000 gallons and still gave me about 40gpm, way more than needed for a 4 bay...

When we disassembled the 2" meter from the main, it had cast iron flanges attached to the copper pipe. The copper pipe was almost completely blocked off at one of the flanges because of galvanic corrosion (Dissimilar Metal Reaction). The 2" copper had a small opening about the size of a dime for flow! It was sheer luck that I discovered this issue. The buildup was on the downstream side of the meter. Luckily my meter is located in the ER and easy to get to. Might be something for you to check out....

Another thing not mentioned and could be easily checked...Do you have a Wye Strainer ahead of the Back Flow Preventer? The screen could be blocked?

 

[Dan-Ark]

Do you have any Cast Iron connected to Copper or Brass in your main water supply? I replaced my 2" meter with a 1" meter to save on minimum water charges...Years ago my wash had an auto in one of the bays which probably needed the 2" main. I was paying based on 33,000 gallons minimum with the 2" supply. ...I don't come close to that even with weep. A 1" meter dropped minimums to about 6,000 gallons and still gave me about 40gpm, way more than needed for a 4 bay...

When we disassembled the 2" meter from the main, it had cast iron flanges attached to the copper pipe. The copper pipe was almost completely blocked off at one of the flanges because of galvanic corrosion (Dissimilar Metal Reaction). The 2" copper had a small opening about the size of a dime for flow! It was sheer luck that I discovered this issue. The buildup was on the downstream side of the meter. Luckily my meter is located in the ER and easy to get to. Might be something for you to check out....

Another thing not mentioned and could be easily checked...Do you have a Wye Strainer ahead of the Back Flow Preventer? The screen could be blocked?

Thanks Good points! No wye strainer. citi dug up the meter to look for a pressure regulator and said the problem was a leak. I think I'll call the city back out to see if they have flow at the meter. I have a hose bib just inside the equipment room and even there the pressure drops as soon as I turn on anything in the wash. I don't think one Hydrominder (dema) opening should drop the pressure any noticable amount and it does...

 

[Greg Pack]

Just thinking off the top of my head- I've had gate valves go bad and stick in an almost closed position. If you have a backflow preventor inside you can screw a gauge on one of the test ports and another somewhere in the equipment room. This will help you determine if the problem is in the line or inside the building.

 

[Randy]

The first thing you want to do is inspect the system for any galvanized pipe or nipples, like 2biz has said they will corrode to the point that you get very little flow through the pipe. Greg has some good advice, check for any half open valves, I’ve seen lot of valves that the gate has come off the stem with the valve partially open. A 100’ run of ¾” pipe at 45 psi will only give you about 18-20 gpm. You lose about 10-12 psi at your backflow preventer. I’d probably remove the backflow preventer and do a flow test to see how much water is coming into the car wash system. I think you might have a problem on the city water side of the water system. What size water meter do you have? How old and what material is the pipe coming into the water meter? Worse case you might have to install a 300 gallon tank and a shallow well pump or replace the water line with a 1” or a 11/4” water line and go to a bigger water meter. My bet it’s something on the city side. But a ¾” water line is too small for a car wash.

 

[Dan-Ark]

Thanks everyone for your insight. This was was originally built as a 2 bay and the third was added at a later date. I;m guessing the 3/4" line was plenty for 2 bays and is obviously marginal at best for 3. I found PVC feeding the cut off valve where it changed to the copper that went under the building, but I have not checked to be sure it is PVC all the way under the driveway back down to the meter. I'll dig that up and also make sure there is not some old regulator or cast iron on that end. Then if nothing obvious there, I'll talk to the water dept again. If they cant do anything, I'll add a pressure tank and if necessary a booster pump. My other wash has an 86 gallon pressure tank that I believe was installed to support the added demand when they added a D&S 5000. that wash has been running 4 SS bays and the D&S on a 1" service and have often had all bays in use so I am thinking something similar might work here. We seldom have 2 bays in use at once and almost never all 3. replacing the service is not very appealing to say the least. The problem with the pressure drop is just as important if not more so than the low flow, as it is affecting the chemical draw and messing up the ratios causing weak mixture in the bays.

 

[Randy]

I'll bet there's some galvanized pipe in the system somewhere or a valve that is partially closed. When was this car wash built?

 

[Dan-Ark]

not sure when it was actually built, but I think the 3rd bay was added in 1989, at least there was some concrete work done and some names and a 1989 date inscribed therein. The guy had built and owned several car washes locally. I think he owned my other wash at some time too. I have no idea what kind of plumbing is on the city side of the meter.

 

[Randy]

It could be a problem on the city side of the meter. I’d still do a flow test at the backflow and probably at the water meter. Do you know what size water meter you have? Is the valve fully open at the meter?

 

[Twodose]

What size is the water companies line that feeds into your ¾” ? I know we had to get the PUC involved to get the local water co in one of our locations to put in a larger line in out in the road.

We had a 1” line on a 4 bay there and it was way undersized, it should have been 1-1/2”.

I think ¾ is to small for a 3 bay, I have a 3 bay now and we ran 1-1/4” to the equipment room, but this is on a well, not city water.

 

[bosswash]

Had similar problems with a 4 bay site built in the 70's. Not enough pressure for hydrominders to work properly, RO would throw low water faults. etc. Installed grundfos Scala 2 booster pump... keeps everything at 80psi. Works perfectly...except they are a little pricey and the build quality is kinda crappy. First one started leaking in 6 months...its replacement has been going for a year.