Pressure Drop in Water Pressure during HP Auto Cycle

[Bubbles Galore]

There is a substantial pressure drop in our dog wash when the automatic is demanding water during the HP rinse passes. Any ideas as to how I can mitigate that type of pressure loss? Would an expansion tank be of any benefit? Our dog wash stays extremely busy and I don't want to alienate any customers due to this pressure loss.

Thanks,

John

 

[pitzerwm]

Since I'm assuming that dog wash pressure is less than city pressure, adding a elevated tank, should absorb that pressure loss.

 

[Bubbles Galore]

I have my dog wash plumbed in at city water pressure.

 

[mjwalsh]

There is a substantial pressure drop in our dog wash when the automatic is demanding water during the HP rinse passes. Any ideas as to how I can mitigate that type of pressure loss? Would an expansion tank be of any benefit? Our dog wash stays extremely busy and I don't want to alienate any customers due to this pressure loss.

Thanks,

John

John,

We put gauges at strategic points of our distribution. It could be after looking at the gauge drop situation at the start of your piping --- if there is no drop there --- that the issue is within how your pipes branch out. That could possibly be the most economical way of correcting the situation.

Back in 1987 when we put in our new car wash bays with smaller tanks in December of that year we were shocked to see the small pump tanks not keeping up --- cavitating our Cat 310 pumps. We had to almost immediately contract out an "under the road job" considering our severe weather to bring in a 4" line rather than a 2" line.

Mike

 

[Waxman]

How about a storage tank for the dog wash, kinda like the automatic has a plastic storage tank that feeds the pump. That way the dog wash can have a reserve to make up for any pressure/volume drop.

 

[mjwalsh]

How about a storage tank for the dog wash, kinda like the automatic has a plastic storage tank that feeds the pump. That way the dog wash can have a reserve to make up for any pressure/volume drop.

Wax,

If I remember right Bubbles-John has a similar extra simple system like Big Leo's & mine. It is reliable but it does require everything to be perfect --- possibly that includes the Watts balancing valve to not have too big of a incoming pressure fluctuation. As far as I know all the turnkey dog wash systems use the same extra simple system --- I could be wrong.

In other words there is no pump. The gravity of a plastic storage tank it seems would not be the same as the proper consistent city water pressure --- which I believe is needed in Bubbles-John's case. I am not sure on a bladder style tank --- exactly if that could solve the fluctuation problem.

Mike

 

[Waxman]

Oh; I thought there was some type of pump on a petwash.

Maybe if the inbay had a bigger feed tank it could fill more slowly, demanding less water in a short time period?

Just an idea.

 

[mjwalsh]

Oh; I thought there was some type of pump on a petwash.

Maybe if the inbay had a bigger feed tank it could fill more slowly, demanding less water in a short time period?

Just an idea.

Wax,

I am not familiar with inbay automatics but if Bubbles-John has the space --- it seems like that would be another potential option. I know our original equipment from 1968 had a huge tank that we got rid of in 1987 --- & it did allow us to have that reserve extra water during fluctuations.

Mike

 

[Bubbles Galore]

Thanks for all the feedback guys. I am thinking about this tank:

http://www.menards.com/main/water-heaters/residential/richmond-10-gallon-electric-6-year-point-of-use-water-heater/p-200187-c-5637.htm

and an expansion tank similar to this:

http://www.menards.com/main/heating-cooling/hydronic-radiant-heat/system-components/5-gallon-expansion-tank/p-212845-c-8523.htm

If a setup like this won't work, I'm not sure what other kind of options I may have. I'm open to any and all suggestions.

 

[Randy]

I’ve seen this many times when you install an inbay automatic and more systems. The incoming water line is undersized for the application. I’ve seen some operators install a booster pump to get more pressure or replace the incoming water main and meter to a larger size. What size meter and water line do you have coming in?

 

[Bubbles Galore]

I've got a 2" coming in from the road.

 

[MEP001]

Another option would be to restrict the valve to the automatic enough to (hopefully) not let it draw enough water that the pressure is affected. If you want to keep the pet wash system water pressure consistent, you might get away with putting a regulator before the feed to it and reducing it lower than the water pressure usually drops.

Have you checked the softener lately? If the resin is breaking down it can cause a loss of flow.

 

[Randy]

I forgot you have a water softener, we don’t have to use them up here in God’s country the water is naturally soft. Measure the pressure differential between the inlet of the water softener and the outlet. Your automatically going to lose about 10 – 15 Psi in the Backflow preventer. What size water meter do you have? I’ve seen contractors/builders install a 5/8” water meter to supply a 2” service. Without being there to see how everything is plumbed it’s hard to guess what is going on

 

[mjwalsh]

Based on actual experience

and an expansion tank similar to this:

http://www.menards.com/main/heating-cooling/hydronic-radiant-heat/system-components/5-gallon-expansion-tank/p-212845-c-8523.htm

If a setup like this won't work, I'm not sure what other kind of options I may have. I'm open to any and all suggestions.

Bubbles-John,

One of the reasons why I did not suggest in my posts which were similar to Randy's suggestion is this: Correct me if I am wrong --- but an expansion tank as in your link is more suitable for a closed loop heating system. I happen to have had many of these types of expansion tanks over the years. For one thing they tend not to be stainless so with fresh domestic water I wonder about rust from it getting into the pet wash water. Usually the air pressure is closer to 12 PSI --- I am not sure what will happen when you charge it at the higher than 40 PSI that --- I am pretty sure that you will need for the Pet Wash that I believe is very similar to mine & Big Leo's.

Having said the above --- it does seem like people on well water have been known to use a type of expansion tank --- there again --- they may be tolerating some momentary rust from time to time --- that you do not want in your pet wash spray.

We made some stainless steel 40 gallon tanks out of stainless steel for the hot water portion of our boiler system because of the poor longevity of the original insulated bladder tanks --- we had gone through almost 10 of them over the years. Not pleasant --- we would walk by & we would get a tiny laser like spray of water in our face --- oh where ... oh where could that water be coming from? Investigation showed a tiny pinhole in the outer jacket --- the bladder had failed & went through the insulation to the steel outer jacket. True story --- happened like I said --- almost 10 times.

mike walsh king koin of bismarck

 

[MEP001]

A 5-gallon expansion tank would do almost no good at all for your problem. The reason the tank is used on a water heater is to allow for the minute expansion of the water when it's heated. If you were to use a bladder tank to allow for the large amount of water used by the auto, it would have to be more than twice the number of gallons the machine uses to refill the tank while the pet wash is having pressure problems. You could get by with a booster pump/bladder tank just for the pet wash supply, but I'd start looking for another problem. Put gauges before and after the backflow preventer and after the softener.

 

[Washmee]

I had a similar problem at my wash. I used one of these, to give the problem area a reserve of water at the pressure I needed. Worked great.

http://www.harborfreight.com/1-horsepower-shallow-well-pump-with-stainless-steel-housing-68387.html

 

[mjwalsh]

I had a similar problem at my wash. I used one of these, to give the problem area a reserve of water at the pressure I needed. Worked great.

http://www.harborfreight.com/1-horsepower-shallow-well-pump-with-stainless-steel-housing-68387.html

Bubbles-John,

I would go for all the rest of the solutions suggested first. When I corrected our low pressure with the larger piping at the pertinent point we also helped the overall situation for other needed fills around our facility. In other words ---- especially if the pressure loss is a factor for the Automatic somehow.

When Washmee-Jon says he has first hand experience with the stainless pump-tank -- it sounds like it could be an option --- much better than your Menards choice. Take heed to the review that says a check valve is a must if you use it. The 50 PSI seems to be on the border of what you need for the Pet Wash Watts Regulator valve --- I am not sure.

Washmee-Jon

I notice on the specs ----- "6.3 gallon hardened steel alloy tank"
That sounds like it is not all stainless steel --- I wonder if your application is less sensitive to small amounts of rusty water than what a Pet Wash would want to allow.

mike walsh king koin of bismarck

 

[Bubbles Galore]

I will need to post a few pictures tonight, but i realized last night that my copper feed line is 3/4" which is reduced down to 3/8" for some reason...if i replumb everything with 3/4" pushlock hose will that help solve the problem? There is still a pressure issue, but will more volume mitigate the back pressure loss?

 

[mjwalsh]

I will need to post a few pictures tonight, but i realized last night that my copper feed line is 3/4" which is reduced down to 3/8" for some reason...if i replumb everything with 3/4" pushlock hose will that help solve the problem? There is still a pressure issue, but will more volume mitigate the back pressure loss?

John,

3/8" for any significant length is like using a longer straw to drink from. Pressure, & volume & cV are definitely related --- even sharp angles are a cV factor. Like Randy & Mep suggested the softener can also be a major cV pressure drop factor.

Mike

 

[bigleo48]

Bubbles,

I have/had the same problem. Installed a booster pump with a regulator that runs when the timers are running. Still drops some, but no complaints as it always remains usable (above 60psi).

But the draw from the HP water tank on my M5 was also causing other problems. With it dropping the building water pressure down from 85PSI to below 30PSI it was causing my water softer tanks and my spot free carbon tank to inflate and deflate... eventually destroying them.

I fixed this by limiting the water pressure to the HP tank down to 45PSI and put a check valve to limit any back pressure. I also put a water pressure regulator set to 45PSI to my spot free system.

All works well now.

Big