ro filling up 5 gallon bucket

Since it's on city water, I'd suggest checking the pressure and tap water TDS, even though pressure shouldn't be such an issue on most municipal water systems. Some of it could just be picking the wrong time of day to make water -- during certain times of the day, the pressure at our house is as high as 100 psi, while there are times during that same day that I've seen it drop to 60 or 70 psi without us running any water in our house. What the neighbors are doing can have a big effect on water pressure. If the TDS is really high, it could be slowing production rate a little bit as well.
 
Are you constantly running short of RO water? If you're only using it for water changes once a week, and you let it run into a holding tank all week, I would think you'd be able to accumulate plenty of water unless you're maintaining some huge tanks. Could you push it to run faster? Sure, but if you don't really need to, spend the money elsewhere.
 
my tds reads no more 40ppm in tap water.

Are you constantly running short of RO water?
yes. i need to make it asap sometimes.

i really think filling up a 5 gallon in 4 hrs its really slow.
 
Have you thought about buying say a 150gal HDPE container for storage? It would probably be cheaper than buying a boost pump and plumbing it in.
 
I have a 100 GPD membrane in mine. I am currently using a 30 gallon well supply tank, with all plastic fittings (Rated for drinking water) in my system. The tank is charged at about 12 PSI, the input pressure to the RO system is about 75 PSI. (through 3/8 tubing, not 1/4) My system runs until the pressure in the well tank reaches about 45PSI, (60% of the input pressure of 75PSI) about 25 gal of water, this is enough for me to do a 20% (actually more, because I mix RO and Non-RO in the tank) water change on my 125, but I also fill 5 gal drinking water bottles from tis setup in about 2 minutes. Might add another tank to double my storage capacity. Check the link in my sig below for some pix of this setup if you like.
 
AquariaCentral.com